ESDU 16004 is a bibliography consisting of a collection of references acquired over the period 1998 to 2016 in relation to the work at ESDU on cavities, initially on drag and subsequently on the more general aspects concerning aerodynamics and aero-acoustics. The work on cavity drag and the early work on cavity aerodynamics and aero-acoustics was specific to rectangular box cavities, since that was the area in which the great majority of the available experimental and theoretical work had been carried out. The later work on cavity aerodynamics and aero-acoustics was able to widen the scope to include cavities of more irregular shapes typical of weapons bays, but for the sake of consistency the titles of the Data Items retained the term "rectangular planform". Although large (more than 1300 references), the bibliography is by no means definitive. In an effort to make the bibliography easier to use, it has been divided into a number of sections, each devoted to a particular subject area. The nine sections are as follows:

A. Cavity Aerodynamics

B. Cavity Acoustics

C. Cavity Drag

D. Cavity Acoustic Suppression (or Control)

E. Store Separation and Trajectory

F. Captive Trajectory System (CTS) and Drop Testing

G. Model Scaling

H. Aircraft/Stores Compatibility

I. Actuators for Suppression (or Control)

The references in each section are listed in date order, one advantage being that it allows the chronological development of a particular subject area to be followed. As an aid to that, the numbering system within each section has three components to identify it. For example: A.61.2, where A denotes the subject area from the above list, 61 is the last two digits of the year of issue (1961 in this example), and 2 is a number identifying the particular reference in any given year (number 2 in this example, from a list of 1, 2, 3 ...). This system has a certain flexibility, another advantage being that it allows subsequent entries to be made without the need for any renumbering. [Note that the first two digits are not given in the reference number; they are either 19 or 20, and since the earliest reference listed is from 1927 there will be no ambiguity until 2027.] There are, of course, many instances of references which cover more than one of the subject areas A to I. Rather than to have an extensive duplication of the entries, they have been included in the one section deemed to be of primary interest. Typical examples of this are mentioned following the title of each of sections A to F of the bibliography.