An alternative classification, based on the pronominal and conjugation systems, was proposed by A.N. Tucker in 1967.
ɐn ɔːltˈɜːnətˌɪv klˌæsɪfɪkˈeɪʃən, bˈeɪst ɔnðə pɹənˈɑːmɪnəl ænd kˌɑːndʒuːɡˈeɪʃən sˈɪstəmz, wʌz pɹəpˈoʊzd baɪ ˈeɪ.ˈɛn. tˈʌkɚɹ ɪn nˈaɪntiːnhˈʌndɹɪd sˈɪksti sˈɛvən.