To select an appropriate fuzzy implication for approximate reasoning under each particular situation is a difficult problem. Although some theoretically supported guidelines are now available for some situations, we are still far from a general solution to this problem.

p. 312 as cited in: William Siler, James J. Buckley (2005) Fuzzy Expert Systems and Fuzzy Reasoning. p. 36. - Fuzzy sets and fuzzy logic (1995)