第19页 2.4 Criteria for phonemic status

So we introduce a further condition: to qualify as allophones of one phoneme, two phones must not only be in complementary distribution, but they must be phonetically similar. This is a tricky criterion; but we can accept it as intuitively plausible, and in practice workable, even if not formally definable.

只是单纯想感慨下Roger Lass作为才子型学者的行文。。。。