Since the reader is presumed to have the general technical background knowledge appropriate to the art, the examiner should not require the applicant to insert anything in the nature of a treatise or research report or explanatory matter which is obtainable from textbooks or is otherwise well-known. Likewise the examiner should not require a detailed description of the content of cited prior documents. It is sufficient that the reason for the inclusion of the reference is indicated, unless in a particular case a more detailed description is necessary for a full understanding of the invention of the application (see also II, 4.18 and III, 2.3a). A list of several reference documents relating to the same feature or aspect of the prior art is not required; only the most appropriate need be referred to. On the other hand, the examiner should not insist upon the excision of any such unnecessary matter, except when it is very extensive (see II, 7.4).