| Type | Book |
| Title | The Written Languages of the World: A Survey of the Degree and Modes of Use |
| Author(s) | |
| Volume | 1 |
| Publication (Day/Month/Year) | 1989 |
| Publisher | International Center for Research on Bilingualism |
| URL | https://books.google.de/books?id=yU8nq-C6wnoC |
| » | India - Census 1971 |
| » | India - Census 1981 |