I have written a paper in mathematics and the journal which I sent my paper has accepted to publish it. I have two references in my article, and they are like:
1- "The proof of Akranov can be found with some additional information in the book of Mikhail Kirkhov ."
2- "We can prove this using the Prime Number Theorem (see  pp.138 for the conclusion from the PNT)..."
My question: Do I have to obtain written permissions from the authors of the books  and ? Is this a copyright issue?