While QUEENSOD solves the full objective function, utilizing only Stirling’s approximation, others have made more drastic
approximations. Some of these, such as those proposed by Willumsen (1980, 1981, and 1984), are widely utilized but
can be shown to introduce considerable error, as will be indicated next. It should be noted that a full description of the
implication of each approximation on the solution is beyond the scope of this paper and will be presented in a forthcoming
publication.