2004, Harold McGee, chapter 13, in On Food and Cooking: The Science and Lore of the Kitchen (in English), Scribner, →ISBN:
There are two basic methods for fermenting beer, and they produce distinctive results. One is rapid fermentation at a high temperature with ale yeasts (strains of Saccharomyces cerevisiae) that clump together, trap the carbon dioxide gas that they produce, and rise to the wort surface.