8. We have selected areas which are both of strategic importance and on which our present knowledge is inadequate. Certain other areas which may be of greater strategic importance but on which we already possess considerable data have been omitted, as reports could be compiled at comparatively short notice. 9. Though future events may, in special circumstances, necessitate certain additions to the list, we appreciate that it is most desirable that alterations should be avoided whenever possible once work on the handbooks has been started.