Bijvank and Vis (in press).
They classify the literature in four categories.
They subsequently discuss continuous review systems with fixed or variable order sizes
(referred to as (s,Q) and (s,S) policies) and periodic review systems
without and with fixed order costs. Their literature review
confirms that there are only a limited number of papers dealing
with lost sales systems and the vast majority of these papers
make simplifying assumptions to make them analytically tract-
able. Out of the 61 papers they identified, 18 papers study
continuous review systems with a fixed order size and the
majority of these papers (13 papers) assume at most 1 (or 2)
orders are outstanding, while four other papers assume lead-time
and/or demand have a specific probability distribution function
(e.g. Poisson). Likewise, out of the eleven papers on continuous
review systems with variable order sizes, i.e. (s,S)-order-up-to
policies, nine papers assume s1⁄4S1. The majority of the 32