Marlin, Chris "Modelling, Comparison and Design", pp1-10

Hingston, P. (1994) Hingston, P. F. (Ed.) Proc. 1994 Western Australian Computer Science Symposium (Claremont, Western Australia, September 1994)  

Languages mentioned 2.PAK {1975} AI language with coroutines. ACL {1980} A Coroutine Language