Timothy Usher, Santa Fe Institute
The Bulum River family consists of two closely-related language, Borong, also known as Kosorong, and Somba-Siawari, also known as Burum-Mindik, spoken south of the Cromwell range from the Bulum river valley in the west to the Kua river in the east and south to the confluence of the Bulum and Mongi rivers in Papua New Guinea's Morobe province Its nearest linguistic relatives are the Mongi River languages to the northeast (McElhanon 1967: 5-6, Suter 2018: 6, q.v. p. 4.)
The internal classification of Bulum River is as follows:
Bulum River
Borong
Somba-Siawari
Siawari
Somba
Burum (Somba) and Mindik (Siawari) were treated as different languages in McElhanon (1967,) but are nowadays considered to be dialects of a single languge.
McElhanon (1967: 6-9) gives lexicostatistical figures between Kosorong (Borong,) Mindik (Siawari) and Burum (Somba) as follows:
| Kosorong | Mindik | Burum | |
| Kosorong | — | 42.1 | 37.1 |
| Mindik | 42.1 | — | 73.6 |
| Burum | 37.1 | 73.6 | — |
Pilhofer (1927-1928) comparative morphology for Somba
Pilhofer (1928-1929) 290 comparative terms for Bulum (Somba)
McElhanon (1967: 34-43) 140 comparative terms for Kosorong (Borong,) Mindik (Siawari) and Burum (Somba)
McElhanon (1968) 1,438 comparative terms for Kosorong, Yakŋe (Siawari) and Burum
McElhanon and Voorhoeve (1970) 67 Trans New Guinea comparisons include examples from Kosorong, Burum and Mindik
McElhanon (2012) 1,993 comparative terms for Yakŋe, Burum and Kosorong
Olkkonen (1982) phonology of Burum (Somba)
Olkkonen and Olkkonen (1983) grammar of Burum (unobtained)
Olkkonen (1985) phonology of Burum
Olkkonen (1987) Somba-Siawari orthography (unobtained)
Olkkonen (1990) Somba-Siawari clitics
Olkkonen (1994) sketch phonology of Mindik
Olkkonen (2000) phonology of Borong
Olkkonen and Olkkonen (2000) grammar of Borong
Olkkonen (2001) sketch phonology of Borong
Olkkonen and Olkkonen (2003) dictionary of Somba-Siawari (unobtained)
Olkkonen and Olkkonen (2004) dictionary of Burum-Mindik
Olkkonen and Olkkonen (2007) dictionary of Somba-Siawari
Smith (1988) Morobe counting systems (unobtained)
Suter (2018) comparative Pindiu grammar including (pp. 43-51) Pindiu object-marking verbs and (pp. 182-188) Pindiu desinences
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Proto-Bulum River had … consonants and … vowels as follows:
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… initial consonants …
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| Bulum River | Kosorong | Borong | Burum | Yakŋe | Somba-Siawari |
| McElhanon | Olkkonen | McElhanon | McElhanon | Olkkonen | |
| *… | |||||
| *… |
… medial consonants …
…
| Bulum River | Kosorong | Borong | Burum | Yakŋe | Somba-Siawari |
| McElhanon | Olkkonen | McElhanon | McElhanon | Olkkonen | |
| *… | |||||
| *… |
… final consonants …
…
| Bulum River | Kosorong | Borong | Burum | Yakŋe | Somba-Siawari |
| McElhanon | Olkkonen | McElhanon | McElhanon | Olkkonen | |
| *… | |||||
| *… |
… vowels and diphthongs …
…
| Bulum River | Kosorong | Borong | Burum | Yakŋe | Somba-Siawari |
| McElhanon | Olkkonen | McElhanon | McElhanon | Olkkonen | |
| *… | |||||
| *… |
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