The republic of uzbekistan ministry of higher and secondary specialized education

1) "Comparative linguistics". Encyclopaedia Britannica. Britannica.com. 2011. Retrieved 23 April 2019.

2) Ringe, D. A. (1995). "'Nostratic' and the factor of chance". Diachronica. 12 (1): 55–74. doi:10.1075/dia.12.1.04rin.

3) See for example Language Classification by Numbers by April McMahon and Robert McMahon

4) Campbell, Lyle (2004). Historical Linguistics: An Introduction (2nd ed.). Cambridge: The MIT Press

5) Greenberg, J. H. (2001). "The methods and purposes of linguistic genetic classification". Language and Linguistics 2: 111–135.