Discuss the different ways in which England could be said to be part of an "empire" at any time between 1066 and 1272.

J. Le Patourel, The Norman Empire (1976) [capital "E"!] and "The Norman Conquest: 1066, 1106, 1154?" in R. Allen Brown (ed.) Proceedings Battle Conference 1978 = Anglo-Norman Studies i (1979) opened up these questions for debate.
Hollister, "Normandy, France & the Anglo-Norman Regnum", Speculum (1976) reprinted in his Monarchy, Magnates & Institutions (1986) looks closely (& very helpfully) at the evidence for lordship links.
J.C. Holt, Colonial England, 1066-1215 (1997) [Temp. Control No.: APH6303] will be right to the point if Olin makes it available in time.
D. Bates, "England & Normandy after 1066", English Historical Review (1989) [Olin, Rm. 601] and J. Green, "Unity & Disunity in the Norman State", Historical Research 62 (1989) assess the degree of integration of government in England and Normandy. David Crouch, William Marshall (1990) surveys the test case of a great man who tried to keep his lands on both sides of the Channel.
J.C. Holt, "The End of the Angevin Realm", Proceedings of the British Academy (1976) reprinted in his Magna Carta & Medieval Government and J. Gillingham, The Angevin Empire (1984) (much in a small space) are both to the point.

A. Duggan, The Devil's Brood takes a novelist's look at Angevin family relations from an excellent knowledge of the chronicles