Stephen Krashen received a PhD. in Linguistics from the University of California, Los Angeles in 1972. He is professor emeritus at the University of Southern California. He is a linguist, educational researcher, and political activist. Krashen has more than 500 publications, contributing to the fields of second-language acquisition, bilingual education, heritage language development and literacy. He is known for introducing several hypotheses related to second-language acquisition, including the acquisition-learning hypothesis, the input hypothesis, the monitor hypothesis, the affective filter, and the natural order hypothesis. Krashen promotes the use of free voluntary reading (including fiction) for second-language acquisition, which he says “is the most powerful tool we have in language education, first and second.” Many of his publications are available for free download. Links at  sdkrashen.com, twitter (skrashen) and researchgate. He was also the 1978 incline bench press champion of Venice Beach, California.