The main result is that two possible structures which may be imposed on an edge symmetric double category, namely a connection pair and a thin structure, are equivalent. A full proof is also given of the theorem of Spencer, that the category of small 2-categories is equivalent to the category of edge symmetric double categories with thin structure.
Theory and Applications of Categories, Vol. 5, 1999, No. 7, 163-175 http://www.tac.mta.ca/tac/volumes/1999/n7/n7.dvi http://www.tac.mta.ca/tac/volumes/1999/n7/n7.ps ftp://ftp.tac.mta.ca/pub/tac/html/volumes/1999/n7/n7.dvi ftp://ftp.tac.mta.ca/pub/tac/html/volumes/1999/n7/n7.psTAC Home