Your search returned the following 2 documents:

2. Codes: Unequal Probabilities, Unequal Letter Cost
   Doris Altenkamp and Kurt Mehlhorn
   In: Automata, languages and programming (ICALP-78): 5th international colloquium, Udine, Italy, 1978, 15-25
   
1. Two Versus One Index Register and Modifiable Versus Non-modifiable Programs
   Kurt Mehlhorn and Wolfgang J. Paul
   In: Automata, languages and programming (ICALP-89) : 16th international colloquium, Stresa, Italy, 1989, 603-609