Every graph occurs as an induced subgraph of some hypohamiltonian graph
Carol T. Zamfirescu, Tudor I. Zamfirescu · Journal of Graph Theory · 2017
Abstract We prove the titular statement. This settles a problem of Chvátal from 1973 and encompasses earlier results of Thomassen, who showed it for K3, and Collier and Schmeichel, who proved it for bipartite graphs. We also show that for every outerplanar graph there exists a planar hypohamiltonian graph containing it as an induced subgraph.