Hansen, Sönke: Partial differential equations : papers presented at Stefan Banach International Math. Center at the semester "Partial differential equations" held Sept. 11 - Dec. 16, 1978 (Banach Center publications / On the "Fundamental Principle" of L. Ehrenpreis. . In: Partial differential equations : papers presented at Stefan Banach International Math. Center at the semester "Partial differential equations" held Sept. 11 - Dec. 16, 1978 (Banach Center publications. Jg.1983, S.185201