3.8 Search on dependent claims 

However, where the patentability of the subject-matter of the independent claim is questioned, it may be necessary for assessing whether the subject-matter of the dependent claim as such is novel and involves an inventive step to continue the search in other sections of the documentation, e.g. in one or more additional classification units. No such special search is made for features that seem prima facie trivial or are generally known in the art. However, if a handbook or other document showing that a feature is generally known can be found rapidly, it may be cited (see G‑VII, 6(iii)). When the dependent claim adds a further feature (rather than providing more detail of an element figuring already in the independent claim), the dependent claim is to be considered in combination with the features in the independent claim and is dealt with accordingly (see F‑IV, 3.4).