1. Lecture Notes in Computer Science;M. Abbott,2003
2. Lecture Notes in Computer Science;M. Bhargava,2005
3. Carboni, A., Lack, S., Walters, R.F.C.: Introduction to extensive and distributive categories. JPAA 84(2), 145–158 (1993)
4. Lecture Notes in Computer Science;K. Chatzikokolakis,2007
5. Cheung, L.: Reconciling Nondeterministic and Probabilistic Choices. PhD thesis, Radboud University Nijmegen (2006)