We also wrote an update in an appendix on Varieties of
Lattices in the 2nd edition of
General
Lattice Theory by George Grätzer, Springer Verlag (1998).
We thank Springer Verlag for publishing the book and allowing us to
put it on the web. (Quote from an email from the Mathematics Editorial
at Springer Verlag: "...the Lecture
Notes volume having indeed been unavailable for some time now, the copyright
has reverted automatically to you and Professor Rose as authors. We have no
objections to making the book available to other researchers in another
form. We ask that the source of the original publication be indicated
explicitly.")