The one-one correspondence means only that if a particular sound 'x' in a given position is associated with a phoneme 'Y' we will associate with it, in the stated position, some sound 'x’', 'x’’', wich is substitutable for the original 'x' (i.e. has the same distribution as 'x').
- Harris (1951), a pag.5

It is empirically discoverable that in all languages which have been described we can find some part of one utterance which will be similar to a part of some other utterance. ‘Similar’ here means not physically identical but substitutable without obtaining a change in response from native speakers who hear the utterance before and after the substitution: e.g the last part of 'He’s in.' is substitutable for the last part of 'That’s my pin'.
- Harris (1951), a pag.20

We equate any two sequences of classes if one of them is substitutable for the other in all utterances in which either occurs.If the sequence of 'A + ly' is always substitutable for 'D', we write the equation 'A ly = D'. This equation means that the range of utterance environments of 'A ly' is identical with that of 'D', or that wherever we find a member of 'D' we may substitute for it not only some other member of 'D' but also some member of 'A' followed by 'ly'.
- Harris (1951), a pag.263