(lax) voice or between modal voice and creaky voice. Languages in the Pearic branch and some in the Vietic branch can have a three- or even four-way voicing contrast. However, some Austroasiatic languages have lost the register contrast by evolving more diphthongs or in a few cases, such as Vietnamese, tonogenesis. Vietnamese has been so heavily influenced by Chinese that its original Austroasiatic phonological quality is obscured and now resembles that of South Chinese languages, whereas Khmer, which had more influence from Sanskrit, has retained a more typically Austroasiatic structure. Proto-language Much work has been done on the reconstruction of Proto-Mon–Khmer in Harry L. Shorto's Mon–Khmer Comparative Dictionary. Little work has been done on the Munda languages, which are not well documented. With their demotion from a primary branch, Proto-Mon–Khmer becomes synonymous with Proto-Austroasiatic. Paul Sidwell (2005) reconstructs the consonant inventory of Proto-Mon–Khmer as follows: This is identical to earlier reconstructions except for . is better preserved in the Katuic languages, which Sidwell has specialized in. Internal classification Linguists traditionally recognize two primary divisions of Austroasiatic: the Mon–Khmer languages of Southeast Asia, Northeast India and the Nicobar Islands, and the Munda languages of East and Central India and parts of Bangladesh, parts of Nepal. However, no evidence for this classification has ever been published. Each of the families that is written in boldface type below is accepted as a valid clade. By contrast, the relationships between these families within Austroasiatic are debated. In addition to the traditional classification, two recent proposals are given, neither of which accepts traditional "Mon–Khmer" as a valid unit. However, little of the data used for competing classifications has ever been published, and therefore cannot be evaluated by peer review. In addition, there are suggestions that additional branches of Austroasiatic might be preserved in substrata of Acehnese in Sumatra (Diffloth), the Chamic languages of Vietnam, and the Land Dayak languages of Borneo (Adelaar 1995). Diffloth (1974) Diffloth's widely cited original classification, now abandoned by Diffloth himself, is used in Encyclopædia Britannica and—except for the breakup of Southern Mon–Khmer—in Ethnologue. Munda North Munda Korku Kherwarian South Munda Kharia–Juang Koraput Munda Mon–Khmer Eastern Mon–Khmer Khmer (Cambodian) Pearic Bahnaric Katuic Vietic (Vietnamese, Muong) Northern Mon–Khmer Khasi (Meghalaya, India) Palaungic Khmuic Southern Mon–Khmer Mon Aslian (Malaya) Nicobarese (Nicobar Islands) Peiros (2004) Peiros is a lexicostatistic classification, based on percentages of shared vocabulary. This means that languages can appear to be