Proceed to Safety

First page . . . Forward to page 3 . . . Last page (page 8)

Origins of the Chuquet Number Names

"Chuquet" number names are the origin of the now-standard -illion-type names for powers of 1000.

The following bit of text is from Nicolas Chuquet, Triparty en la Science des Nombres (1484) and presents the "powers of a million" number-naming system in its original form:

original words of Chuquet apparently transcribed
original words of Chuquet apparently transcribed

[...] pr[oc]eder. ¶ Item lon doit savoir que ung million vault mille milliers de unitez, et ung byllion vault mille milliers de millions, et [ung] tryllion vault mille milliers de byllions, et ung quadrillion vault mille milliers de tryllions et ainsi des aultres. Et de ce en est pose ung exemple : nombre divise et punctoye ainsi que devant est dit, tout lequel nombre monte 745324 tryllions 804300 byllions 700023 millions 654321. Exemple : 745324'8043000'700023'654321.
   ¶ Addition.

Middle French: [...] to go. Item: one should know that a million is worth a thousand thousand units, and a byllion is worth a thousand thousand millions, and [a] tryllion is worth a thousand thousand byllions, and a quadrillion is worth a thousand thousand tryllions, and so on for the others. And an example of this follows, a number divided up and punctuated as previously described, the whole number being 745324 tryllions 804300 byllions 700023 millions 654321. Example : 745324'8043000'700023'654321.
      ¶ Addition.

As you can see, Chuquet intended the names to represent powers of 1000000 (the long scale or "billion=1012 system"). It is also clear that he was using prefixes that came from Latin, either directly or indirectly through French. To the more scientific mind it is more logical to use billion for 10000002, trillion for 10000003 and so on. In his example number there is an extra 0 that does not belong, 8043000 should be 804300. I suspect that the text pictured is a copy and that the error was introduced during transcription.

The immediately preceding line of text, not seen in the image, establishes Chuquet's use of number-names as high as nonillion and implied proposal to use Latin number prefixes for higher number-names "as far as you wish to go":

Ou qui veut le premier point peult signiffier million Le second point byllion Le tiers poit tryllion Le quart quadrillion Le cinqe quyllion Le sixe sixlion Le sept.e septyllion Le huyte ottyllion Le neufe nonyllion et ainsi des ault's se plus oultre on vouloit pr[oc]eder. [...]

French: Or if you prefer the first mark can signify million, the second mark byllion, the third mark tryllion, the fourth quadrillion, the fifth quyillion, the sixth sixlion, the seventh septyllion, the eighth ottyllion, the ninth nonyllion and so on with others as far as you wish to go. [...]

Possibly in 1514, but definitely by 1516, Guillaume Budé (or Guilielmus Budaeus in Latin) in the book De Asse et partibus ejus, discussed the number of horsemen in Revelation 9:15-16. In Greek it is Δύο μυριάδιεσ μυριάδιωμ, Duo myriadies myriadium. Then he discusses "decem myriadum myriadas" (ten myriad myraids, i.e. 109), saying that quod uno verbo nostrates abaci studiosi Milliartum appellant ("which our abacus students call in one word Milliart"). Unfortunately the same sentence ends with quasi millionum millionem, possibly leading to confusion.

In any case, this writing introduced the word Milliart (milliard) for 109 and the word spread with the help of Jacques Peletier du Mans. As I mentioned, the words quasi millionem millionum, "like a million millions"; led some including Wikipedia to believe this "milliart" was somehow associated with 1012; nevertheless the use of milliard for 109 clearly emerges in the late 1600's.

Triparty en la Science des Nombres was copied and published by Estienne de La Roche in the 1520 textbook l'Arismetique, without attribution to Chuquet. 1520 is the date given by French dictionaries for the origin of the word billion9, but trillion is properly dated as coming from 1484.

Some History of Short vs. Long Scale

(A more thorough history is presented in the Wikipedia article Long and short scales.)

During the 17th century7 it became common practice in France to divide digits into groups of 3, and during this time billion began to be used as the name for 109 in France and Italy. French mathematicians decided to switch to this usage because they found it easier.2

From around that period came this quote, which has sometimes been placed alongside Chuquet's name or the above image, but is from a later writer:

Au lieu de dire mille milliers, on dira million, au lieu de dire mille millions, on dira byllion, etc..., et tryllion, quadrilion ... octylion, nonyllion, et ainsi des autres si plus oultre on voulait proceder.
French: Instead of saying one thousand thousands, one may say million; instead of saying one thousand millions, one may say billion, etc..., and trillion, quadrillion, ... octillion, nonillion, and others as far beyond as you wish to go.

This passage reflects the short scale (or "billion=109") system. This meaning of the word billion came to the British American colonies (what would become the United States) in the early 1700's, and became common in France during the early 1800's (though France later switched back, in the mid 1900's).

The Chuquet number names were adopted throughout Europe (with minor spelling changes for each language), and used for both systems causing ambiguity when texts were translated. The billion=1012 system was adopted in England, Germany, Spain, Scandanavia, and eastern Europe except Russia8. Throughout the 1800's the French usage of the billion=109 system gained influence in the United States. As the world became larger and nations more interdependent, the ambiguity became an ever-greater problem, particularly when large amounts of money were being discussed.

Chuquet's manuscript was discovered by Aristide Marre in the late 1870s and published in 18802,6.

In 1922 came Fowler's A Dictionary of Modern English Usage; the entry on the usage of "billion" points out that this was 109 in France and the United States (i.e. short scale), and 1012 in Great Britain (long scale); also curiously noting that the word billion for 1012 "is useless except to astronomers, it is a pity that we do not conform" [by having that word mean 109]. This is perhaps a hint as to why it really did not matter at the time that there were two systems in use. (The Dictionary's entry on the words "atom, molecule, nucleus, proton, neutron, electron" has a few paragraphs on that new scientific topic which was evidently alien to almost all writers at the time, and hints at what is to come when it needs to explain that 100,000,000 atoms in a line would measure about an inch.)

In France, the 1948 General Conference on Weights and Measures deprecated the billion=109-system senses of the words billion through sextillion in favor of the billion=1012 system and this suggestion became official in 1961 throughout the French-speaking world (septillion and the higher number names were never part of the French language). France had finally2 switched back to the original version of the number names she had created.

But the influence of the billion=109 system, primarily from the United States, was so great that by 1974, the Prime Minister of the U.K. announced that the billion=109 system was to be used for all official communications, effectively completing a transition that had long been taking place among the general population in English-speaking countries.

Latin Number Names

This table of Latin number names is adapted from several sources (16, 26, 36, 37, 38, 39). They can be used to formulate a system of number names extending on the Chuquet names. It will be useful as a reference when considering the proposals of writers throughout the 1800's and 1900's. Of these, the most consistent and well-researched is the Conway-Wechsler system from [51] (1995).

Arabic Roman Latin
1 I unus, una, unum primus
2 II duo, duae, duo secundus ; alter
3 III tres, tres, tria tertius
4 IV quattuor quartus
5 V quinque quintus
6 VI sex sextus
7 VII septem septimus
8 VIII octo octavus
9 IX novem nonus
10 X decem decimus
11 XI undecim undecimus
12 XII duodecim duodecimus
13 XIII tredecim tertius decimus
14 XIV quattuordecim quartadecimus ; quartus decimus
15 XV quindecim quintadecimus ; quintus decimus
16 XVI se(x)decim sextus decimus
17 XVII septemdecim septimus decimus
18 XVIII duodeviginti duodevicesimus
19 XIX undeviginti undevicesimus
20 XX viginti vice(n)simus
21 XXI viginti unus ; unus et viginti vicesimus primus
22 XXII viginti duo ; duo et viginti duoetvicesimus; vicesimus alter ; vicesimus secundus
23 XXIII viginti tres ; tres et viginti vicesimus tertius
24 XXIV viginti quattuor ;
(etc.: there is a similar
[units] et [tens] form for
each number below 100)
quartavicesimus (?) ; vicesimus quartus
25 XXV viginti quinque vicesimus quintus
28 XXVIII duodetriginta duodetricesimus
29 XXIX undetriginta undetricesimus
30 XXX triginta trice(n)simus ; trigesimus
38 XXXVIII duodequadraginta
39 XXXIX undequadraginta
40 XL quadraginta quadrage(n)simus
50 L quinquaginta quinquage(n)simus
60 LX sexaginta sexage(n)simus
70 LXX septuaginta septuage(n)simus
80 LXXX octoginta octoge(n)simus
90 XC nonaginta nonage(n)simus
98 XCVIII nonaginta octo ; duodecentum 26 duodecentesimus
99 XCIX nonaginta novem ; undecentum 26 undecentesimus
100 C centum centesimus
122 CXXII centum viginti duo centesimus vicesimus secundus
200 CC ducenti, -ae, -a ducentesimus
300 CCC trecenti, -ae, -a trecentesimus
400 CCCC quadringenti, -ae, -a quadringentesimus
500 D quingenti, -ae, -a quingentesimus
600 DC sescenti, -ae, -a sescentesimus
700 DCC septingenti, -ae, -a septingentesimus
800 DCCC octingenti, -ae, -a octingentesimus
900 DCCCC nongenti, -ae, -a nonagentesimus
1000 M mille millesimus
1124 MCXXIV mille centum viginti quattuor
2000 MM duo milia bis millesimus
3200 MMMCC tria milia ducenti
10,000 X decem milia
100,000 C centum milia
200,000 CC ducenta milia
1,000,000 decies centena milia

Chuquet's Dubious Use of Latin

To those with a reasonable working knowledge of the Latin language, or anyone looking at the higher Latin numbers (as listed above) and comparing them later authors' extensions of the names beyond Chuquet's nonyllion, it becomes clear that Chuquet was not consistent in his use of any particular language to form prefixes. One might impugn the whole idea that Latin was the only source (perhaps it was French, or hallucination?).

Many of the following are Numeral prefixes used in familiar words like tricycle and quadruped.

ncardinalmultipleordinal French Italian Chuquet
2 duo bi-/bis- secundus deux due b(y) + llion
3 tres/tria ter- tertius trois tre tr(y) + llion
4 quattuor quater- quartus quattuor quattro quadr(i) + llion
5 quinque quintus cinq cinque qu(y) + llion
6 sex sextus six sei six + lion
7 septem septimus sept sette sept(y) + llion
8 octo octavus huit otto ott(y) + llion
9 novem nonus neuf nove non(y) + llion

The closest match to Chuquet's choice is highlighted in bold. Note that bis means "twice" in Latin, and is likely the origin for "byllion".

Chuquet Names in the 1800s

In 1826, Dudley Leavitt published the book Pike's System of Arithmetick, beginning with a "Numeration" section describing how numbers are represented in print. The names millions, billions, trillions, etc. through duodecillions are used for powers of 1000000 (i.e. Leavitt used the "long scale") and always appeared in the plural, e.g. "Eight hundred millions three hundred forty-four thousand and two hundred". You can read the relevant text here: Dudley Leavitt, Pike's System of Arithmetick, 1826.

In 1856, Noble Heath published his A Treatise on Arithmetic, including a table of Latin number-names and examples of how to make these into names of powers of 1000 as high as centillion. You can read the relevant text here: Noble Heath, A Treatise on Arithmetic, 1856. This may well have been a personally-derived extension of the names up to duodecillion that were published in English at least as early as 1826 (Leavitt).

The earliest concerted effort I know of started with a "Professor Henkle" (most probably William Downs Henkle, from Ohio and born in 1828), whose ideas for number-names up to milli-millillions=106000000 first appear in an 1860 edition of The Ohio Educational Monthly. He begins with a survey of earlier names (by Pike, Greenleaf, Loomis, Heath, Ray, Thomson, Holbrook) and discussion of the Latin derivation pointing out that the names are based on ordinal, not cardinal numbers (e.g. "quintillion" comes from quintus not quinque). A list of names is given, containing enough examples to infer that the system is meant to allow constructing a name for any power of 1000000. You can read the full text of the article here: W. D. Henkle, Names of the Periods in Numeration, 1860.

106000000 is Henkle's largest single named power of 10, "milli-millillion", and that name became more well-known than all the rest. (The original article gives the name milli-millions to the 1000000th power of 1000000; the following issue has an erratum correcting it to "milli-millillions".) He clearly states that The names of the periods after millions denote the respective powers of a million, i.e. long scale. (Most subsequent usage uses short scale, i.e. a milli-millillion is 103000003.)

Ad-hoc Chuquet Extensions

(and personal -zillion name systems)

As described above, the commonly accepted number names like trillion come from Chuquet. It had already been established in Chuquet's time that prefixes based on Latin cardinal number-names would be used to express powers of a million, and the influence of Chuquet and Peletier was enough to cement an agreement to continue with that method as far as was wanted or needed.

As seen by comparing the Latin names above with the post-Chuquet standard powers of 1000, there are discrepancies even in a few of the names found in the highly-regarded print dictionaries: while tredecillion matches the Latin word tredecim, octodecillion departs completely from the Latin word for 18, which is duodeviginti. These discrepancies are similar to those Chuquet himself established with e.g. quintillion vs. Latin quinque=5 (omitting the que part of quinque).

Henkle points this out, in noting that "quintillion"/"sextillion"/"nonillion" clearly have far greater resemblance to the Latin ordinals quintus/sextus/nonus. (If they had been based on the cardinals quinque/sex/novem, we would have something like "quinquillion"/"sexillion"/"novillion".) Henkle therefore suggests using Latin cardinal syllables throughout; but others before and after Henkle had difficulty, as the numbers get higher the Latin ordinals become less definitive and more awkward.

Things get a little worse when going beyond vigintillion because there is no good Latin prefix for twenty-one. Just as in English, starting with 21 the name for the number goes to two words, with the smaller part as the second word. Those who have extended Chuquet names beyond vigintillion usually go to something like unvigintillion, breaking away from the Latin but keeping the similarity to undecillion. This is what was done in the excellent work of John H. Conway and Allan Wechsler as described here. For example, in the short scale, the Conway and Wechsler name for 1090 is novemvigintillion, but I have also seen vigintinonillion apparently based on some combination of the cardinal viginti "twenty" and ordinal nonus "ninth"23 despite that undetriginta and undetricesimus were by far the most common way to say "29" and "29th" in Latin.

The question of whether to use elision (omitting letters for more natural pronunciation) results in the distinction between sexdecillion and sedecillion for 1051, tresvigintillion and trevigintillion for 1072, and so on.

There seems to be a cult-like appeal to the Chuquet number names, evident in the fact that many people have been inspired to create systems, and none seem to want to use each other's system. In this regard the Chuquet extension phenomenon resembles the cult of 137 that has built up around the Sommerfeld fine-structure constant. What follows is a partial survey of personal, "ad-hoc" Chuquet-like naming systems that have been created over the years, with relevant links.

Henkle's names were re-published in 1876 by Edward Brooks, then again in 1904 [42]. These were listed in 1968 by Dmitri Borgmann [45] in the premiere issue of his Word Ways: the Journal of Recreational Linguistics. By that point it seems no-one knew who "Henkle" was [53], though it should have still been apparent that his knowledge of the Latin language was adequate for the task.

The Borgmann article sparked several follow-on articles in Word Ways presenting Chuquet-like extension proposals, notably Rudolf Ondrejka in 1968 [46] (who proposed a system that goes up to milli-millimillillion=103000000003, full text here); and John Candelaria [47],[48] (who redefined milli-millimillillion to be 103×103000000+3 and topped out at nona-centillillesillillion=103×102700000000+3; see texts from 1975, 1976, and 1983).

In the fall 1980 presentation of Stanford's CS 204, Donald Knuth and Allen Miller presented some problems relating to alphabetical ordering of numbers.30 In this they defined 10213 to be septagintillion rather than the more commonly-seen septuagintillion; similarly 10243 was octagintillion rather than octogintillion.

John Knoderer has created a set of number names between vigintillion and centillion, differing somewhat from the above. For example, he gives septoctogintillion for 10264, whereas the Conway-Wechsler name is septemoctogintillion His names are listed on his Numbering Systems & Place Values page. Sally Berriman provides a similar list.

Gregg William Geist 23 applied Latin names more strictly than most others, even going so far as to adapt the standard Latin undeviginti=19 into the name undevigintillion for 1060, and similarly undetrigintillion for 1090, etc. He also puts the bigger part first for everything above vigintillion: vigintimillion=1066, vigintisextillion=1081, centumsedecillion=10351, etc.

Russ Rowlett has proposed a more original system based on Greek prefixes. His main stated goal is to avoid the ambiguity of the existing Latin-based names entirely by replacing them all. He starts with gillion for 109 inspired by the SI prefix giga-, then uses Greek number names as prefixes: tetrillion=1012, pentillion=1015, hexillion=1018, ... icosillion=1060, ..., triacontillion = 1090, and so on. The Greek number prefix corresponds to the power of 1000, thus tetr- for 4, and tetrillion=10004.

Louis Epstein uses SI-like prefixes (e.g. kilillion=10000001000=106000, zetillion=106×1021) reminiscent of some of the smaller Bowers names for certain class-3 numbers, and also combines multiple Greek parts with Latin parts in elaborate ways. For example, he states 5 that "The 1048576th power of a million is a sexseptaginquinhectooctoquatriginkilmegillion" (emphasis added); the hecto, kil and meg parts come from Greek while the other parts are the familiar Latin syllables used in most of the other systems.

These systems have plenty of differences, and frequently even ambiguity or lack of self-consistency. Going beyond 103003 (or 106000 in the "long scale") allows for even more variations, mainly from the use of a large number of prefixes strung together and having to remember what order they go in. Perhaps to address this issue, Landon Curt Noll supplements his extensive article "How high can you count?" with a page that automaticlly converts numbers to names, with downloadable source code for UNIX users like me. A few examples of his system: 1019683 is "one sexmilliaquingensexagintillion", 103000003 is "one milliamilliatillion", and 101010 = 1010000000000 is "ten tremilliamilliamilliatrecentretriginmilliamilliatrecentretriginmilliatrecendotrigintillion". His system has a name for googolplex that is two words long, "ten tremilliamilliamillia...milliatrecentretriginmilliatrecendotrigintillion"; the second word has 3903 letters.

It gets far worse when trying to name numbers large enough that the number of digits exceeds 101000000 — but ad-hoc Chuquet devotees have tried. Jonathan Bowers tackled this with a massive profusion of prefixes and syllables with combination rules, with four tiered systems roughly corresponding to the naming of numbers in class 2 through class 5 respectively. This page by googologist Sbiis Saibian41 describes it in detail. The largest lexical building block in the system is 103×103×103×1045−3+3, with the name "nonecxenulti-nonecxenersi-nonecxenupi-nonecxenaxi-nonecxenoci-nonecxeneti-nonecxenoli-nonecxenovi-nonecxenermi-nonecxenuni-nonecxenasti-nonecxeniji-nonecxeneji-nonecxenali-nonecxenillion".

Despite their impracticality, and the existence of the impeccably-researched, systematic, backwards-compatible, and endlessly extensible system of Conway and Wechsler, other people keep making up their own Chuquet-like systems even to this day. However, by the early 2000s it seems that this area had begun to decline in popularity, with the efforts of most ad-hoc creators largely shifting to the much wilder terrain of rapidly-growing function hierarchies and invented 'googol'-like names. Perhaps Conway-Wechsler has gained enough popularity to make it a harder target to beat.

More Conway-Wechsler Number Names

The following table shows examples of extensions to the Chuquet names using the most consistent and well-researched extension (that by Conway and Wechsler in [51], including the Miakinen suggestion regarding quin-). The rightmost column shows how some others have dealt with the task of turning the Latin into a prefix.


NN in Latin 3,17 103N+3 Conway-Wechsler name [51] for 103N+3 other names
12duodecim 1039duodecillion dodecillion24
13tredecim 1041tredecillion tertio-decillion25
14quattuordecim 1045quattuordecillion quarto-decillion25
15quindecim 1048quindecillionquinquadecillion19
16sedecim ; sexdecim 1051sedecillion sexdecillion18,30
18duodeviginti 1057octodecillion duodevigintillion23
19undeviginti 1060novendecillion novemdecillion18, undevigintillion23
20viginti 1063vigintillion vigillion25
21viginti unus ; unus et viginti1066unvigintillionprimo-vigillion25
22viginti duo ; duo et viginti 1069duovigintilliondovigintillion24
25viginti quinque ; etc. 1078quinvigintillion quinquavigintillion19
27viginti septem 1084septemvigintillion septenvigintillion32
28duodetriginta 1087octovigintillion
29undetriginta 1090novemvigintillion vigintinonillion23,undetrigintillion23
30triginta 1093trigintillion
32triginta duo 1099duotrigintillion dotrigintillion24
33triginta tres 10102trestrigintillion tretrigintillion24
35triginta quinque 10108quintrigintillion quinquatrigintillion19
40quadraginta 10123quadragintillion
45quadraginta quinque 10138quinquadragintillion quinto-quadragintillion23
47quadraginta septem 10144septenquadragintillion
50quinquaginta 10153quinquagintillion
55quinquaginta quinque 10168quinquinquagintillion
61sexaginta unus 10186unsexagintillion
70septuaginta 10213septuagintillion septagintillion30
80octoginta 10243octogintillion octagintillion30
86octoginta sextus 10261sexoctogintillion
99nonaginta novem ; undecentum 26 10300novenonagintillion
100centum 10303centillion
101centum unus 10306uncentillion primo-centillion25
102centum duo 10309duocentillion
103centum tres 10312trescentillion
113centum tredecim 10342tredecicentillion tertio-decimo-centillion25
116centum sedecem 10351sedecicentillion centumsedecillion23
121centum viginta unus 10366unviginticentillion primo-vigesimo-centillion25
133centum triginta tres 10402trestrigintacentillion
180centum octoginta 10543octogintacentillion octogesimo-centillion25
200ducenti/ae/a 10603ducentillion same25
207ducenti septem 10624septenducentillion
300trecenti 10903trecentillion same25
333trecenti triginta tres 101002trestrigintatrecentillion
560quingenti sexaginta 101683sexagintaquingentillion
600sescenti 101803sescentillion sexcentillion25
806octingenti sex 102421sexoctingentillion
999undemille(?) 103000novenonagintanongentillion
1000mille 103003millinillion millillion25
1001mille unus 103006millimillion
1002mille duo 103009millibillion
1003mille tres 103012millitrillion
1013mille tredecim 103042millitredecillion
1234mille ducenti triginta quattuor 103705milliquattuortrigintaducentillion
6560sexies milia quingenti sexaginta 1019683sextillisexagintaquingentillion
19683undevicies milia sescenti octoginta tres 1059052novendecillitresoctogintasescentillion
1000000decies centena milia 103000003millinillinillion milli-millillion25

The Conway-Wechsler system disagrees with some dictionaries regarding quinquadecillion, sedecillion, and novendecillion (which are better known as quindecillion, sexdecillion and novemdecillion respectively)18,20,21. Miakinen22 explains that sedecillion and novendecillion are more true to the "rules of assimilation" in Latin, and thus the Conway-Wechsler version is better. But he also explains that quinquadecillion should be quindecillion because the Latin for 15 is "quindecim", not "quinquadecim", and proposes a similar change to all the Conway-Wechsler names involving the quinqua- prefix; I have adopted his suggestion here.

Notably, they are identical to the Henkle names for many values of 10300N+3 up to millillion.

Beyond 103000, the Conway-Wechsler system combines multiple parts of the names for smaller numbers to form a name for the larger number. The rules are described here. In the table above, you can see several more examples. A convenient pattern emerges: 103006 is one millimillion, which combines an extra milli- with the familiar name million for 106. Similarly, 103009 is millibillion, 103000 times a billion, and so on.

This pattern continues all the way up: compare the names above for 101683 and 1019683: they differ only by the addition of an initial sextilli- which is derived from sextillion. sextillion is 1021, and sextilli- is found at the beginnings of Conway-Wechsler names up to 1021000 (and starting with 1018003).

Successful use of the Conway-Wechsler system depends on careful attention to the details of the assimilation rules for combining multiple prefixes. For example, someone could conclude that 10312 trescentillion and 10903 trecentillion had the same name. However, if the rules are followed completely (as described here) there are no spelling ambiguities. (Pronunciation, however, is still an issue!)

Also of note is Wechsler's comment:

The presentation in The Book of Numbers was designed to leave the impression that the system up to 999 was pre-existing, although in fact we invented a lot of it; you will note that Conway carefully never says the system is ancient. -- Allan Wechsler21

Although Conway's book does state (emphasis added):

You can now use the usual rules for combining this complete system of zillion words (which first appears in the present Book of Numbers) so as to obtain correct 'English names', like [...] -- Conway and Guy [51]

Perhaps their system will trip up one or two future etymology researchers, but the inconsistency with quindecillion, sexdecillion and novemdecillion should make the truth obvious.

First page . . . Forward to page 3 . . . Last page (page 8)

Robert Munafo's home pages on AWS    © 1996-2024 Robert P. Munafo.    about    contact
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Details here.