@incollection{compref216,
   author = {Lofgren,L},
   year = {1973},
   title = {On the Formalization of Learning and Evolution},
   booktitle = {Logic, Methodology and the Philosophy of Science IV},
   editor = {Suppes,P and Henkin,L and Joja,A and Moisil,GC},
   publisher = {North-Holland},
   address = {Amsterdam},
   pages = {}
}