Hamiltonian cycle theory and network reliability.
- My early research was in network reliability and basic graph theory. Since 1985 it has focused on hamilton cycles and long cycles in graphs; in particular, the relationship between the toughness of a graph and its cycle structure
- In the last few years my work has focused on matchings in graphs and the properties of Tutte sets. I have also studied the computational complexity of recognizing toughness in various classes of graphs, as well as finding maximum Tutte sets
- I am currently working on the interplay between the connectivity of a graph and its cycle structure.