Antonio Blanco Enrique Freire Brañas José Luis Freire Javier París The Foldl Operator as a Coequalizer Using Coq. 167-176 2009 EUROCAST http://dx.doi.org/10.1007/978-3-642-04772-5_23 conf/eurocast/2009 db/conf/eurocast/eurocast2009.html#BlancoBFP09