for all x, y£L. It is easily shown that every join-endomorphism is an isotone correspondence (i.e. x^y implies ®x=i 8y). It is also easy to see that the set / of antecedents of 0 under any join-endomorphism is an ideal. (For these and other facts used in the sequel we refer to the textbook of G. Birkhoff, Lattice theory, rev. ed., New York, 1948, henceforth cited as LT.) G. Birkhoff states in L...