Esperanto in the Declaration of Boulogne at the first World Esperanto Congress later that year. However, in his 1888 Aldono al la Dua Libro (Supplement to the Second Book), he officially altered the spelling of the suffixes of the temporal correlatives (when, then, always, sometimes, never) from -ian to -iam, which rendered the Esperanto of Unua Libro slightly outdated. Content The book consists of three parts, an introduction, a grammar section, and a dictionary. Zamenhof begins by renouncing all rights to the language, putting it in the public domain. In the introduction, Zamenhof lays out his case for the need for an international auxiliary language (IAL). He states that previous attempts, such as Volapük, have failed because they have not overcome the three main difficulties an IAL must overcome in order to succeed. Those difficulties are: In the next three parts, he addresses each difficulty specifically and explains why he believes Esperanto is fit to overcome them. In part I, he explains the simplicity and flexibility of Esperanto grammar, particularly due to its regularity and use of affixes. In part II, he demonstrates the ease of using Esperanto for international communication due to a simple and clear vocabulary. To demonstrate this, he translates the Our Father and Genesis 1:1–9 and presents a fictional letter and a few poems in Esperanto—"El Heine'", a translation, and "Mia penso" and "Ho, mia kor'", both original. In part III, he presents an idea called the "universal vote", which is a campaign to allot 10 million signatures of people making the following pledge: "I, the undersigned, promise to learn the international language, proposed by Dr. Esperanto, if it shall be shown that ten million similar promises have been publicly given." He argues that this will prevent anyone from wasting time on learning the language since, once 10 million signatures have been gathered, there will be a significant population obliged to learn the language, rendering the language useful. He also welcomes critical feedback for the next year and promises to consider criticism before publishing a special booklet that will give definitive form to the language the following year (which was to be Aldono al la Dua Libro). Additionally, he lays out guidelines for a language academy to guide the evolution of the language in the future (which was to be the Akademio de Esperanto). In the grammar section, he explains the Esperanto alphabet and sixteen grammar