Schempp, W. / Zeller, K. (eds.), Multivariate Approximation Theory. Proceedings of the Conference held at the Mathematical Research Institute at Oberwolfach, February 1979. Basel-Boston-Stuttgart, Birkhäuser Verlag 1979. 455 S., 49 Abb., sFr. 58,–. DM 64,–. $ 38.00. ISBN 3-7643-1102-9 (ISNM 51) and Schempp, W. / Zeller, K. (eds.), Multivariate Approximation Theory II. Proceedings, Oberwolfach, February 8–12, 1982. Basel-Boston-Stuttgart, Birkhäuser Verlag 1982. 429 S., DM 68,–. ISBN 3-7643-1373-0 (ISNM 61)