doi          = "10.1002/malq.19810270205",
 doi          = "10.1145/1292597.1292602",
 doi          = "10.1145/1596627.1596631",
 doi          = "10.1007/3-540-36576-1\_16",
 doi          = "10.1145/964001.964025",
 doi          = "10.1145/1352582.1352591",
 doi          = "10.1145/1328438.1328483",
 doi          = "10.1145/345099.345100",
 doi          = "10.1145/292540.292560",