[3] In the Okinawa-go jiten (1963), Uemura Yukio simply left its subgroups flat: Several others have attempted to create intermediate groups.

He first presented a flat list of dialects and then discussed possible groupings, one of which is as follows: The difference between the two hypotheses is whether Southern Amami and Northern Okinawan form a cluster.

Thorpe (1983) presented a "tentative" classification similar to Uemura's:[4] Karimata (2000) investigated Southern Amami in detail and found inconsistency among isoglosses.

Nevertheless, he favored the three-subdivision hypothesis: Karimata (2000)'s proposal is based mostly on phonetic grounds.

Unlike Northern Amami and Southern Okinawan, Southern Amami and Northern Okinawan tend to maintain labiality, though the degree of preservation varies considerably.

Uemura (1972) also argued that if the purpose of classification was not of phylogeny, the two-subdivision hypothesis of Amami and Okinawan was also acceptable.

[3] Lawrence (2011) argued that lexical evidence supported the Kikai cluster although he refrained from determining its phylogenetic relationship with other Amami dialects.

[9] Heinrich et al. (2015) refers to the subdivisions of Northern Ryukyuan as only "Amami" and "Okinawan".