1. Embedding digraphs on orientable surfaces;Bonnington;J. Combin. Theory Ser. B,2002
2. C.P. Bonnington, M. Conder, J. Sneddon, A Kuratowski theorem for clustered planarity (in preparation)
3. Sur les problèmes des courbes gauches en topologie;Kuratowski;Fundamenta Math.,1933
4. Planarity and duality of finite and infinite graphs;Thomassen;J. Combin. Theory Ser. B,1980
5. J. Sneddon, Minors and planar embeddings of digraphs, Ph.D. Dissertation, University of Auckland, 2004