Another criterion is the parallelism of allophones among phonemes. If the allophones of English /p, t, k/ are all analogous in that they have comparable differences of aspiration in identical environments (as [pʰ, tʰ, kʰ] after word-juncture but [p, t, k] after /s/, etc.), we can say that a particular component 'γ' is contained in each of them and that this 'γ' (which may be the combination of the unvoicing and the stop components) is strongly aspirated after word-juncture, unaspirated after /s/, etc.
- Harris (1944), a pag.200