Hans-Jürgen Bandelt Martin Farber Pavol Hell Absolute Reflexive Retracts and Absolute Bipartite Retracts. 9-20 1993 44 Discrete Applied Mathematics 1-3 db/journals/dam/dam44.html#BandeltFH93 http://dx.doi.org/10.1016/0166-218X(93)90219-E