Tense and Aspect (Stanford Encyclopedia of Philosophy)
https://plato.stanford.edu/entries/tense-aspect07.01.2014 · Tense, Mood and Aspect, entry in Wikipedia. Chapter on Tense and Aspect, in the World Atlas of Language Structures Online. A Bibliography of Tense, Verbal Aspect, Aktionsart, and Related Areas,, by Robert I. Binnick. Tenses, Moods and Aspects, Questionnaire by the Max Planck Institute for Evolutionary Anthropology.