It is possible to perform upon the elements various operations, such as classification or substitution, which do not obliterate the identifiability of the elements but reduce their number or make the statement of interrelations simpler.
- Harris (1951), a pag.17

In some cases of classification it is not essential to select one of the members as primary in respect to the other members classified with it. E.g. in grouping complementary segments into one morpheme, we may regard one member as representing the morpheme, and call the other members positional variants of that member in stated positions. Alternatively, we can regard the morpheme as a class of members, all equally limited to particular positions.
- Harris (1951), a pag.307, n.14

The basic operations are those of segmentation and classification […]. Classification is used to group together elements which substitute for or are complementary to one another.
- Harris (1951), a pag.367

The classifications and other operations are always based on relevant (distributional) relations the expression of which leads to a simplification at some point in the final statement. The operations are not intended to classify elements merely for cataloguing convenience (as in the alphabetic ordering in the dictionary), or for convention, or for assignment of names to phenomena or groups of elements.
- Harris (1951), a pag.372, n.16