Is it farther or further?
A subset of PLANNER, implemented in Lisp by Gerald Sussman et al at MIT. Its important features were goal-oriented, pattern-directed procedure invocation, an embedded knowledge base, and automatic backtracking.
microPLANNER was superseded by Conniver.
["microPLANNER Reference Manual", G.J. Sussman et al, AI Memo 203, MIT AI Lab, 1970].