1. A new class of order types;Baumgartner;Ann. Math. Logic,1976
2. Sean Cox, Ph.D. Dissertation, University of California, Irvine, 2009
3. Canonical functions, non-regular ultrafilters and Ulam’s problem on ω1;Deiser;J. Symbolic Logic,2003
4. Some exact equiconsistency results in set theory;Harrington;Notre Dame J. Formal Logic,1985
5. R.B. Jensen, Nonoverlapping extenders, Handwritten Notes, Oxford