Peter Saveliev is a professor of mathematics at Marshall University, Huntington WV, USA. He has devoted the last 25 years to teaching and writing college mathematics. He has also been involved in research in algebraic topology and several other fields, as well as: digital image analysis, automated fingerprint identification, and image matching for missile navigation/guidance.
The textbooks are based on the classes he teaches and, consequently, are constantly updated and improved.
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His channel on YouTube: Lectures on College Mathematics.