Diophantus geometra siue Opus contextum ex arithmetica et geometria simul : in quo quæstiones omnes Diophanti, quæ geometrice solui possunt, enodantur tum algebricis, tum geometricis rationibus. Adiectus est
Paris: Michel Soly, 1660. Rare first edition of this work on the indeterminate problems of Diophantus’ Arithmetica. Billy corresponded actively with Fermat on number theory, and it is mainly through his collection of letters from Fermat, published as ‘Doctrinae Analyticae Inventum Novum’ in the 1670 edition of Bachet’s Diophantus, that we know of Fermat’s methods for solving Diophantine
