The International Code of Zoological Nomenclature (ICZN) is both a book containing (among others) a set of rules and recommendations on the formal naming of animals, and that set itself. Among zoologists (and in the book) it is often referred to simply as "the Code" (in mixed company, taxonomists refer to it as "the ICZN"). It was first published in 1961, although it has precedents going back to 1842; the present edition is the fourth edition (1999). The Code is issued by the International Commission on Zoological Nomenclature. As the Commission may alter the Code without issuing a new edition of the book, it is not necessarily so that the book contains the actual provision that applies in a particular case.