Dear student
A literary source is anything that has been "written" that you cite as your source material. It could be a poem, an historical document, a private letter, a book, a short story, a magazine article, an analysis that has been published, etc.
Sources for study of Indian history:
1. Historians obtained the information on Indian history from various sources.
2. Some accounts of medieval Indian history were from Persian accounts which were different from modern Persian (e.g. the term “Hindustan” did not include south India within it till the time of Babur).
3. Coins, architecture, inscriptions and textual records provided information of the events happened during 700 to 1750 CE. E.g. manuscripts became broadly available.
Regards