Hardy, G. H., & Wright, E. M. (1998). Introduction to the theory of numbers.- 4th ed. (4th ed.). Clarendon Press ; Oxford University Press.

Hardy, G. H., and Edward Maitland Wright. Introduction to the Theory of Numbers.- 4th Ed. 4th ed. Oxford : New York: Clarendon Press ; Oxford University Press, 1998.

Hardy, G. H., and Edward Maitland Wright. Introduction to the Theory of Numbers.- 4th Ed. 4th ed. Clarendon Press ; Oxford University Press, 1998.