When the search report cites documents already mentioned in the description of the patent application for which the search is carried out, these are denoted by the letter "D" (see B‑IV, 1.3).[Rule 42(1)(b); ]
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/b_x_9_2_7.htm
Date retrieved: 17 May 2021