"Morphological opacity does not exist, because purely morphological rules do not exist; all so-called morphological rules are either syntactic, phonological, or a combination of the two." Discuss.
Bierwisch, Syntactic features in morphology (pdf)
Di Sciullo, Morphological phases (pdf)
Dillon, Metaphony as morpheme realization, not vowel harmony (pdf)
Green 2004, Opacity in Tiberian Hebrew: Morphology, not phonology (pdf)
Kiparsky, The morphology of the Basque auxiliary (pdf)
Kurisu, Double morphemic exponence as morphological opacity (pdf)
Pescarini, Prosodic restructuring and morphological opacity (pdf)