Dag Normann Christian Rordam The Computational Power of <i>Mu</i><sup>omega</sup>. 117-124 2002 48 Math. Log. Q. 1 http://dx.doi.org/10.1002/1521-3870(200201)48:1<117::AID-MALQ117>3.0.CO;2-J db/journals/mlq/mlq48.html#NormannR02