Longer essays may also contain an introductory page that defines words and phrases of the essay's topic. Most academic institutions require that all substantial facts, quotations, and other porting material in an essay be referenced in a bibliography or works cited page at the end of the text. This scholarly convention helps others (whether teachers or fellow scholars) to understand the basis of facts and quotations the author uses to support the essay's argument and helps readers evaluate to what extent the argument is supported by evidence, and to evaluate the quality of that evidence. The academic essay tests the student's ability to present their thoughts in an organized way and is designed to test their intellectual capabilities.
Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide , and thereby turns wort into beer. In addition to fermenting the beer, yeast influences the character and flavour.  The dominant types of yeast used to make beer are Saccharomyces cerevisiae , known as ale yeast, and Saccharomyces pastorianus , known as lager yeast; Brettanomyces ferments lambics ,  and Torulaspora delbrueckii ferments Bavarian weissbier .  Before the role of yeast in fermentation was understood, fermentation involved wild or airborne yeasts, and a few styles such as lambics still use this method today. Emil Christian Hansen , a Danish biochemist employed by the Carlsberg Laboratory , developed pure yeast cultures which were introduced into the Carlsberg brewery in 1883,  and pure yeast strains are now the main fermenting source used worldwide.