Phil Ehlers was a postgraduate student (1989-1993) at Bangor, working in the team of [[Ronnie Brown]] and [[Tim Porter]], who was Phil's doctoral supervisor. ## Selected writings On [[simplicial groupoids]] (thanks are due to [[Stephen Gaito]] for preparing a scanned version with Phil's permission): * [[Philip J. Ehlers]], _Simplicial groupoids as models for homotopy type_, Master's thesis (1991) [[pdf](https://ncatlab.org/nlab/files/Ehlers-MSc-thesis.pdf)] also known as [[sSet]]-[[enriched groupoids]]: * [[Philip J. Ehlers]], *Algebraic Homotopy in Simplicially Enriched Groupoids*, PhD thesis, University of Wales Bangor (1993) [[[Ehlers-thesis.pdf|pdf:file]]] He has published several papers based on his work (jointly with Tim Porter). These include: * [[Phil Ehlers|P. J. Ehlers]] and [[Tim Porter]], _Joins for (Augmented) Simplicial Sets_, Jour. Pure Applied Algebra, 145 (2000) 37-44 ([arXiv](http://arxiv.org/abs/math.CT/9904039)) . * [[Phil Ehlers|P. J. Ehlers]] and [[Tim Porter]], _Varieties of simplicial groupoids, I, Crossed complexes_, Jour. Pure Applied Algebra, 120 (1997) 221 - 233; Erratum: Jour. Pure Applied Algebra, 134 (1999) 221-233. * [[Phil Ehlers|P. J. Ehlers]] and [[Tim Porter]], _Ordinal subdivision and special pasting in quasicategories_, Advances in Math. 217 (2007), No 2. pp 489-518. category: people [[!redirects Philip Ehlers]] [[!redirects Philip J. Ehlers]]