b) Do not say words lake adequate evidence.
3) Maxim of relation
  Be relevant.
4) Maxim of manner
  Be perspicuous:
a) Avoid obscurity of expression;
b) Avoid ambiguity;
c) Be brief (avoid unnecessary prolixity)
d) Be orderly.
Grice's Cooperation Principle explains the discourse of the literal meaning and its practical meaning, which is a significant breakthrough in pragmatics. However, Grice’s Conversational Implication can't give full explanation to the fact that we should abide by Cooperation principle, but sometimes we violate it to express ourselves.（Leech, 1983） 广告英语的语用策略分析(2):http://www.youerw.com/yingyu/lunwen_8815.html