Yoshikawa introduced the basic classification system of the Sumerian verb according to their hamtu/maru stem in a 1968 paper. There he proposed a so-called affixation class, the maru class of whose verbs was derived simply by suffixing a particle -e to the hamtu base. This became known as the maru -e. Yoshikawa saw this -e embedded in the so-called '-ed' morpheme, arguing that it was actually a compound /-e/ + /-d/. As a result, analyzed the pronomial maru suffixes (-en, -e, -enden, -enzen, and -ene) into the maru -e plus reduced forms (i.e. -e + -n, -0, -nden, -nzen -ne).

Edzard, on the other hand, argued for a different analysis, in which the maru -e was actually part of the pronomial suffixes used in the maru conjugation. Yoshikawa's affixation class subsequently consisted of verbs whose stem did not change between hamtu and maru (unveranderung klasse).

Edzard, 1971 Hamtu, Maru, und freie Reduplikation….

Yoshikawa, 1968 Maru and Hamtu aspects

Yoshikawa, 1974 The Maru Conjugation in the Sumerian Verbal System