Free-lattice functors weakly preserve epi-pullbacks

H. Peter Gumm, Ralph Freese

Suppose $p(x,y,z)$ and $q(x,y,z)$ are terms. If there is a common "ancestor" term $s(z_1,z_2,z_3,z_4)$ specializing to $p$ and $q$ through identifying some variables \begin…