Grierson, Philip. Byzantine Coinage, 2nd ed. Dumbarton Oaks Byzantine Collection Publications. Washington, DC: Dumbarton Oaks, Trustees for Harvard University, 1999.
Grierson, Philip. Numismatics. Oxford: Oxford University Press, 1975.
Dumbarton Oaks has a number of valuable resources including an online database of their coin collection and PDFs of their published catalogues.