A copy of the fifth edition of the Essais with Montaigne's own "C" additions in his own hand exists, preserved at the Municipal Library of Bordeaux (known to editors as the "Bordeaux Copy").  This edition gives modern editors a text dramatically indicative of Montaigne's final intentions (as opposed to the multitude of Renaissance works for which no autograph exists). Analyzing the differences and additions between editions show how Montaigne's thoughts evolved over time. Remarkably, he does not seem to remove previous writings, even when they conflict with his newer views.
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.