Applying G\"odel's Dialectica Interpretation to Obtain a Constructive   Proof of Higman's Lemma
  We use G\"odel's Dialectica interpretation to analyse Nash-Williams' elegant but non-constructive "minimal bad sequence" proof of Higman's Lemma. The result is a concise constructive proof of the lemma (for arbitrary decidable well-quasi-orders) in which Nash-Williams' combinatorial idea is clearly present, along with an explicit program for finding an embedded pair in sequences of words. 
Thomas Powell (Queen Mary, University of London, United Kingdom)
cs.LO cs.DM