Dirichlet proved that any arithmetic progression without trivial obstructions contains infinitely many primes. His name permeates the introductory study of analytic number theory. In 1850, he was described by a contemporary as follows: "He is a rather tall, lanky-looking man, with moustache and beard about to turn grey, with a somewhat harsh voice and rather deaf. He was unwashed, with his cup of coffee and cigar. One of his failings is forgetting time, he pulls his watch out, finds it past three, and runs out without even finishing the sentence."
Dedekind edited Dirichlet's lectures on number theory and published these as Vorlesungen uber Zahlentheorie in 1863. It is noted by H. M. Edwards that: "Although the book is assuredly based on Dirichlet's lectures, and although Dedekind himself referred to the book throughout his life as Dirichlet's, the book itself was entirely written by Dedekind, for the most part after Dirichlet's death."
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