"It is not until the middle of the fifth century or a little later that a book trade can be said to have existed in Greece: we find references to a part of the Athenian market where books can be bought (Eupolis fr. 327 K.-A.) and Socrates is represented by Plato as saying in his Apology 26D that anyone can buy Anaxagorus' works for a drachma in the orchestra. All details of the trade, however, remain unknown" (Reynolds & Wilson, Scribes and Scholars, 3rd. ed.  2).