doi          = "10.1145/1018203.1018205",
 doi          = "10.1007/978-3-642-23397-5\_22",
 doi          = "10.1109/ASAMA.1999.805390",
 doi          = "10.1145/237721.237805",
 doi          = "10.1007/3-540-46425-5\_1",
 doi          = "10.1007/978-3-540-69611-7\_17",
 doi          = "10.1145/2048066.2048111",
 doi          = "10.1145/1854273.1854313",