The history of the popes from the close of the middle ages : drawn from the secret archives of the Vatican and other original sources. Vol. 27.: Gregory 15. and Urban 8. (1621-1644) / from the German of Ludwig, Freiherr von Pastor ; translated and edited by Ernest Graf
. – London : Kegan Paul, Trench, Trubner, 1938
. – XXXVIII, 336 p. ; 23 cm