Gupta, P.L. & T.R. Hardaker. Punchmarked Coinage of the Indian Subcontinent - Magadha-Mauryan Series. (Mumbai, 2014).
This revision updates the well-known reference from the 1985 first
edition. The GH catalogue numbers have been extended while retaining
the earlier numbers for specific coins, each series better explained,
more photographs of coins posted, and the discussion expanded to include
more topics.
The index of punchmarks now makes it easier to look up specific marks and find out which coins have that mark.