Groeg, O. J. (1979). Who's who in technology: Ed. Austria, Germany, Switzerland ; a biographical encyclopedia / ed. by Otto J. Groeg. Who's who Book u. Publ. Ges..

Groeg, Otto J. Who's Who in Technology: Ed. Austria, Germany, Switzerland ; a Biographical Encyclopedia / Ed. by Otto J. Groeg. Wörthsee b. München: Who's who Book u. Publ. Ges., 1979.

Groeg, Otto J. Who's Who in Technology: Ed. Austria, Germany, Switzerland ; a Biographical Encyclopedia / Ed. by Otto J. Groeg. Who's who Book u. Publ. Ges., 1979.