Are there papers or books that explain why Bernhard Riemann believed that his hypothesis is true? I would like to know what are the mathematical reasons for which Bernhard Riemann believed that his hypothesis is true, and I would like to know if those mathematical reasons were cited in his original paper.
My question Here : Are there papers or books or links that explain why Bernhard Riemann believed that his hypothesis is true?
Note: I do not want to know if the Riemann Hypothesis is true or false.
Thank you for any help 

Harold Edwards provides some informed speculation on this question in his book.  I'm not home right now but will come back and summarize his thoughts in a couple days.
And by the way his book is a gem. It includes a translation of the original paper, and one of the more enjoyable and satisfying couple months of my "mathematical life" was spent working my way carefully through that paper ( it invites lots of side-trips and explorations along the way... I had a particularly long sidetrack with the gamma function... )
