Feng Cheng 0002 Michael Menzel Christoph Meinel A Secure Web Services Providing Framework Based on Lock-Keeper. 375-384 2007 conf/apnoms/2007 APNOMS http://dx.doi.org/10.1007/978-3-540-75476-3_38 db/conf/apnoms/apnoms2007.html#ChengMM07