Dr. Esperanto's International Language (), commonly referred to as (First Book), is an 1887 book by Polish ophthalmologist L. L. Zamenhof, in which he first introduced and described the constructed language Esperanto. First published in Russian on , the publication of Unua Libro marks the formal beginning of the Esperanto movement. Writing under the pseudonym "Dr. Esperanto", Zamenhof originally referred to the language as the international language; the use of Esperanto did not arise until 1889 when people began to use his pseudonym as the name of the language itself. Zamenhof reproduced a significant portion of the content of Unua Libro in the 1905 Fundamento de Esperanto, which he established as the sole obligatory authority over Esperanto in the Declaration of Boulogne, ratified by the first World Esperanto Congress later that year. History After many years of developing the language, Zamenhof completed Unua Libro by the spring of 1885 and spent the next two years looking for a publisher. In 1887, shortly after he married his wife Klara, his new father-in-law Aleksandr Silbernik advised him to use money from Klara's dowry to find a publisher. Following his advice, Zamenhof found a publisher in Warsaw, Chaim Kelter. On , Kelter published the book in Russian as International Language (). Before the end of the year, Kelter published the Polish, French, and German editions of the book, as well. In 1888, Zamenhof had Julian Steinhaus translate the book into English, and the translation was published under the title Dr. Esperanto's International Tongue. However, when Richard Geoghegan pointed out that Steinhaus's translation was very poor, Zamenhof destroyed his remaining copies and requested that Geoghegan produce a fresh translation. Geoghegan's translation of the book, titled Dr. Esperanto's International Language, was published on and became the standard English translation. Henry Phillips, Jr., a secretary of the American Philosophical Society and early supporter of Esperanto, also produced a translation in 1889, titled An Attempt towards an International Language, but Geoghegan's translation remains the preferred standard. Unua Libro was also translated into Hebrew, Yiddish, Swedish, and Lithuanian in 1889 and then into Danish, Bulgarian, Italian, Spanish, and Czech in 1890. The name Unua Libro was applied retroactively to the book in relation to the title of Zamenhof's 1888 book Dua Libro (Second Book). In 1905, Zamenhof reproduced much of the content of Unua Libro in Fundamento de Esperanto, which he established as the only obligatory authority over