@Article{Giles:2015:AAI,
  author =       "Michael B. Giles",
  title =        "Algorithm 955: Approximation of the Inverse {Poisson} 
                  Cumulative Distribution Function",
  journal =      "{ACM} Transactions on Mathematical Software",
  volume =       "42",
  number =       "1",
  accepted =     "24 November 2014",
  upcoming =     "true", 
  abstract =     "
                  New approximations for the inverse of the incomplete
                  gamma function are derived, and these are used to develop
                  efficient evaluations of the inverse Poisson cumulative
                  distribution function. An asymptotic approximation based on
                  the standard Normal approximation is particularly good for
                  CPUs with MIMD cores, while for GPUs and other hardware
                  with vector units a second asymptotic approximation
                  based on Temme’s approximation of the incomplete gamma
                  function is more efficient due to conditional branching
                  within each vector. The accuracy and efficiency of the
                  software implementations is assessed on both CPUs and GPUs.",
}