Kalidasa is most famous for being a Sanskrit playwright who wrote plays based on stories from Hindu scripture. But Kalidasa also composed epic poetry on the same subject, most notably Raghuvamsa, an epic poem about members of the Raghu dynasty, including Rama.
My question is, what are the specific Hindu scriptures that Raghuvamsa is based on? Did Kalidasa ever mention what sources he relied upon to compose it? Or have later scholars surmised where the content of Raghuvamsa originates from?
I assume that the Valmiki Ramayana was one of the sources used, particularly the Uttara Kanda, but what other sources were used?