Employ hyphen to indicate the way in which morphemes are connected with each other. A form which always occurs initially is followed by a hyphen. A form which always occurs finally is preceded by a hyphen. Forms which never occur initially or finally are preceded and followed by hyphens.
- Nida (1949), a pag.11

Hyphens are employed to indicate (1) the relative order of the allomorphs and (2) the fact that the allomorphs occur only in combination.
- Nida (1949), a pag.77