Algorithm AS 204: The Distribution of a Positive Linear Combination of χ 2 Random Variables
R. W. Farebrother · Journal of the Royal Statistical Society Series C (Applied Statistics) · 1984
R. W. Farebrother, Algorithm AS 204: The Distribution of a Positive Linear Combination of χ2 Random Variables, Journal of the Royal Statistical Society. Series C (Applied Statistics), Vol. 33, No. 3 (1984), pp. 332-339