Felix Joachimski Ralph Matthes Short proofs of normalization for the simply- typed lambda-calculus, permutative conversions and Go"del's T. 59-87 2003 42 Arch. Math. Log. 1 http://dx.doi.org/10.1007/s00153-002-0156-9 db/journals/aml/aml42.html#JoachimskiM03