Definition: In this task, a passage will be given and the goal is to identify an event from the passage. An event is defined as a single word representing something that happened, is happening, or may happen. An event can be factual or hypothetical, positive or negative, certain or uncertain. While most events are based on verbs, an event can also be based on a noun (ex. storm, snow, rainfall) or a copula verb (is, was, been, etc.). The event must not be a pronoun or an adjective. For noun events with multiple words, use the last word in the phrase as event.
Input: Passage: The collection, in 240,000 words, consists of more than 70 prose, written by Gao during 1980 to 2003, on the natural conditions, social customs and history of the Sub-Sahara Africa. Gao worked in Africa for more than seven years.

written