1. Gossler, A., Doetschman, T., Korn, R., Serfling, E. & Kemler, R. Proc. natn. Acad. Sci. U.S.A. 83, 9605–9069 (1986).
2. Pascoe, W. S., Kemler, R. & Wood, S. A. Biochim. biophys. Acta 1114, 209–221 (1992).
3. Robertson, E. J. in Teratocarcinomas and Embryonic Stem Cells: A Practical Approach (ed. Robertson, E. J.) 71–112 (IRL, Oxford, 1987).
4. Nagy, A. et al. Development 110, 815–821 (1990).
5. Nagy, A. & Rossant, J. in Practical Approach Series: Gene Targeting (ed. Joyner, A. L.) (Oxford University Press, Oxford, 1993).