[...] the Paradigm Function theory might seem to afford two different conceptions of rules of referral. First, one might assume that a rule of referral encompasses whole words [...]. Alternatively, one might assume that rules of referral encompass the individual steps by which a fully inflected word is built up from the root of its inflectional paradigm.
- Stump (2004), a pag.111

In Paradigm Function theory four types of rules are distinguished: MORPHOLEXICAL RULES (rules of exponence), RULES OF REFERRAL, PARADIGM FUNCTIONS, and MORPHOLEXICAL FUNCTIONS. The formats for these types of rules are given in 9-12. (9) Format for morpholexical rules: MLR“n”,[τ]("x")="y" CLASS: X; (10) Format for rules of referral: RR“n”,[τ]([σ])=[σ]/[F1:v1,..., F“m”:v“m”] CLASS: X; (11) Format for paradigm functions: PF[σ]("x")="y"; (12) Format for morpholexical functions: MLF“n”,[σ]("x")="y").
- Stump (2004), a pag.103