“Some preliminaries (page 22)

The second feature is definitely not open to disregard. This is the requirement, central to the construction of our INTRODUCTION, to substantiate all factual assertions. A factual assertion is simply anything that could prompt your reader to ask 'who says?'. Anything that could be re-written as 'it was found that' or 'it was argued that' or 'it was claimed that' etc., can be regarded as a factual assertion and requires substantiation. You are expected to tell the reader at least by whom it was found (argued, or claimed) and when. So, if you make a firm statement about any aspect of the psychological universe (however trivial), you must attempt to support it.”