@phdthesis{Liu:2011:TPC:2338289, author = {Liu, Hai}, advisor = {Hudak, Paul}, title = {The Theory and Practice of Causal Commutative Arrows}, year = {2011}, isbn = {978-1-124-81060-7}, note = {AAI3467550}, publisher = {Yale University}, address = {New Haven, CT, USA}, }