He wrote several standard works , including The Acting Leader , with Margret Dietrich and Wolfgang Greisenegger which has been revised and reissued .
Gregor was one of the leading theater scholars of his time .
Gregor wrote several standard works , including The Acting Leader , with Margret Dietrich and Wolfgang Greisenegger which has been revised and reissued .
Gregor was one of the leading theater scholars of his time .