The three most spoken international auxiliary languages, Ido, Esperanto, and Interlingua, all use the comma as the decimal separator. Interlingua has used the comma as its decimal separator since the publication of the in 1951. Esperanto also uses the comma as its official decimal separator, while thousands are separated by non-breaking spaces: . Ido's "Kompleta Gramatiko Detaloza di la Linguo Internaciona Ido" (Complete Detailed Grammar of the International Language Ido) officially states that commas are used for the decimal separator while full stops are used to separate thousands, millions, etc. So the number 12,345,678.90123 (in American notation) for instance, would be written "12.345.678,90123" in Ido. The 1931 grammar of Volapük by Arie de Jong uses the comma as its decimal separator, and—somewhat unusually—uses the middle dot as the thousands separator (12·345·678,90123).