Is the Examiner obligated to cite all relevant references he discovers during his search?

MPEP 904 states: The examiner is not called upon to cite all references that may be available, but only the “best.” (See 37 CFR 1.104(c).) Multiplying references, any one of which is as good as, but no better than, the others, adds to the burden and cost of prosecution and should therefore be avoided.