A declaration concerning the newly invented art of double writing Wherein are expressed the reasons of the authors proceedings in procuring a priviledge for the same - Petty, William (Printed by R.L. for R.W. at the Star under Saint Peters Church in Cornhill, 1648)
Annotation on Thomason copy: "Aprill 29.". - Anonymous. Attributed to Sir William Petty. - Kress Lib. S.944. - Reproduction of the original in the British Library. - Thomason, E.437[23]. - Wing (2nd ed.), P1917