Another claim for early democratic institutions comes from the independent "republics" of India, "sanghas" and "ganas", which existed as early as the 6th century B.C. and persisted in some areas until the 4th century. The evidence for this is scattered, however, and no pure historical source exists for that period. In addition, Diodorus—a Greek historian who wrote two centuries after the time of Alexander the Great's invasion of India—mentions, without offering any detail, that independent and democratic states existed in India. Modern scholars note the word "democracy" at the time of the 3rd century B.C. and later suffered from degradation and could mean any autonomous state, no matter how oligarchic in nature.