Although explicit references in the claims to features elucidated in the description or in the drawings are only permissible where "absolutely necessary" (cf. GL/PCT‑EPO F‑IV, 4.17), if claims contain such references, the examiner should strive to search these technical features as long as they are unambiguously defined by specific parts of the description.
However, where the reference does not clearly identify which subject-matter of the description and/or drawings is to be considered as included in the claim, the examiner may informally contact the applicant for clarification before the search is carried out (see GL/PCT‑EPO B‑VIII, 3.3). In the special case of "omnibus claims" (e.g. a claim reading "The invention substantially as herein described"), no request for informal clarification should be issued, and subsequently the search report will be designated as complete.
The procedure above should be followed regardless of whether or not the reference to the drawings and/or the description is allowable according to Rule 6.2(a).
Where the reference does not appear to be justified, the examiner should raise an objection in the written opinion.