[1] Gregor wrote several illustrated pamphlets like the one published in 1930 and titled: Wiens letzte große Theaterzeit ("Vienna's Last Great Theater Epoch").Originally recommended by Zweig, Joseph Gregor wrote three librettos for Richard Strauss: Friedenstag (1938), Daphne (1938) and Die Liebe der Danae (1944), as well as contributing to the texts of Capriccio (1942) and the posthumous school opera Des Esels Schatten.Strauss was planning in 1940, at the suggestion of Heinz Drewes and Hans Joachim Moser, to collaborate with Gregor on a reworked libretto for the opera Jessonda.When Gregor offered to rewrite the text of the opera Die schweigsame Frau to replace Stefan Zweig's libretto, Strauss refused and also withdrew from the Jessonda project.He wrote several standard works, including the periodical titled Schauspielführer with Margret Dietrich and Wolfgang Greisenegger, both of whom went on to prestigious careers as theater scholars at the University of Vienna.