1. Thompson, P. et al. Nat. Neurosci. 4, 1253–1258 (2001).
2. Plomin, R., DeFries, J. C., McClearn, G. E. & McGuffin, P. Behavioral Genetics 4th edn. (Worth, New York, 2001).
3. Kosslyn, S. & Plomin, R. in Psychiatric Neuroimaging Research: Contemporary Strategies (eds. Dougherty, D., Rauch, S. L. & Rosenbaum, J. F.) 491–515 (American Psychiatric Press, Washington, DC, 2001).
4. Vernon, P. A., Wickett, J. C., Banzana, P. G. & Stelmack, R. M. in Handbook of Intelligence (ed. Sternberg, R. J.) 245–264 (Cambridge Univ. Press, 2000).
5. Pennington, B. C. et al. J. Cogn. Neurosci. 12, 223–232 (2000).