Linked from
The 20 pages that link to Proto-Slavic, each with the reason it gives.
Slavic languagesNarrower topic: It is the source language from which the Slavic branches developed.
Polish languageNarrower topic: Polish descends from Proto-Slavic through the West Slavic branch.
Slovak languageNarrower topic: Slovak ultimately descends from this common Slavic ancestor.
Slovene languageNarrower topic: Slovene descends from Proto-Slavic through the South Slavic branch.
South SlavsNarrower topic: South Slavic languages descend from this ancestral language.