1. S. S. Abhyankar, On the valuations centered in a local domain,Amer. J. Math.,78 (1956), 321–348.
2. ——, Resolution of singularities of arithmetical surfaces, pp. 111–152, inArithmetical Algebraic Geometry, New York, Harper and Row, 1965 (edited byO. F. G. Schlling).
3. M. Artin, Some numerical criteria for contractability of curves on algebraic surfaces,Amer. J. Math.,84 (1962), 485–496.
4. ——, On isolated rational singularities of surfaces,Amer. J. Math.,88 (1966), 129–136.
5. N. Bourbaki, Algèbre commutative, chap. 5–6,Act. Sci. et Ind., no 1308, Paris, Humann, 1964.