1. Radtke, F. & Clevers, H. Self-renewal and cancer of the gut: Two sides of a coin. Science 307, 1904–1909 (2005)
2. Molofsky, A. V., Pardal, R. & Morrison, S. J. Diverse mechanisms regulate stem cell self-renewal. Curr. Opin. Cell Biol. 16, 700–707 (2004)
3. Strasburger, M. Bau, Funktion und Variabilität des Darmtractus von Drosophila melanogaster Meigen. Zeit. f. wiss. Zool. 140, 539–649 (1932)
4. Wigglesworth, V. The Principles of Insect Physiology (Methuen & Co. Ltd, London, 1965)
5. Miller, A. in The Biology of Drosophila (ed. Demerec, M.) 420–442 (Hafner, New York, 1950)