2.6 End of search 

Efficiency dictates that the search division use its judgement to end its search once the probability of discovering any more relevant prior art becomes very low in comparison to the work involved. It can also stop its search once it has found documents which clearly demonstrate that the entire subject-matter of the claimed invention and its embodiments in the description lack novelty, except for features which are trivial or common general knowledge in the relevant field and whose application would not involve any inventive step. As to the search for conflicting applications, see B‑VI, 4.