On the courtesy of the author, this page gives a link to a letter from Christopher Lutz to Rolf Landauer (JANUS: A Time-Reversible Language, 1986).
@unpublished{Lutz86,
author = {Christopher Lutz},
title = {Janus: a time-reversible language},
note = {{\it Letter to R.\ Landauer}.},
year = {1986},
}