doi          = "10.1007/978-3-540-69166-2\_10",
 doi          = "10.1145/263699.263744",
 doi          = "10.1145/582153.582176",
 doi          = "10.1007/3-540-36384-X\_13",
 doi          = "10.1109/LICS.1999.782600",
 doi          = "10.1109/LICS.2006.41",