The Hector Hodler Library in Rotterdam, which is devoted to this artificial language, has over 15,000 books
... Perhaps; but as a matter 
of cold fact, Zamenhof's language has been used all over the world for more... [DOC] [TLE] sesa kajero [PAR] It is well known that Zamenhof developed his language Lingvo universala at .... 
Esperanto has been an item of controversy among its grammarians.