Martin Bunzl, ‘Counterfactual History: A User’s Guide’, at: http://www.historycooperative.org/journals/ahr/109.3/bunzl.html plus the online discussion of this article
John Keegan, ‘How Hitler could have won the war’, in Robert Cowley (ed.), What if? Military historians imagine what might have been (1999), pp. 295-309, and ‘Introduction’
Niall Ferguson, ‘One among many’, in Times Literary Supplement, 21 September 2007, book review of Ian Kershaw, Fateful Choices. Ten decisions that changed the world 1940-1941 (2007)
The serious stuff:
‘Introduction: Virtual History: Toward a ‘Chaotic’ Theory of the Past’, in Niall Ferguson (ed.), Virtual History: Alternatives and Counterfactuals (1998).
Johannes Bulhof, ‘What If? Modality and History’, in: History and Theory, Vol. 38, No. 2. (May, 1999), pp. 145-168 [JSTOR]
Mandel D.R, ‘Effect of counterfactual and factual thinking on causal judgements’ in Thinking & Reasoning, Volume 9, Number 3, August 2003 , pp. 245-265 [online – go through UL catalogue]
The hard-core stuff:
Robin Cowan, Dominique For a, ‘Evolutionary economics and the counterfactual threat: on the nature and role of counterfactual history as an empirical tool in economics’, in: Journal of Evolutionary Economics (2002), 539-562 [online – go through UL catalogue]
Gary King, Lagche Zeng, ‘When Can History Be Our Guide? The Pitfalls of Counterfactual Inference’, in: International Studies Quarterly 51 (2007), pp. 183-210 [UL, West Room, p/hole: C.8 — otherwise SW5 P214.c.335]