Variable and Non-spherical Stellar Winds in Luminous Hot Stars Proceedings of the IAU Colloquium No. 169 Held in Heidelberg, Germany, 15-19 June 1998 - Wolf, Bernhard; Wolf, Bernhard; Stahl, Otmar; Stahl, Otmar; Fullerton, Alex W.; Fullerton, Alex W. (Springer Berlin Heidelberg : Imprint: Springer, 1999)