One of the nicest thing about Hindi-Urdu is that, because an enormous amount of work was done it it by British linguists as the British colonial apparatus attempted to get a handle on this vast lingua-franca understood from Kabul to Dhaka and Gilgit to Bombay, there is a vast amount of high-quality work on which copyright has now lapsed. It is available for free on the web.
- Urdu/Hindi: an artificial divide : African heritage, Mesopotamian roots, Indian culture and British imperialism, Abdul Jamil Khan, Algora Publishing, 2006. Google preview, Amazon listing.
- An introduction to the Hindustani language: grammar, vocabulary, short sentences and stories in Persian and Nagari characters, John Shakespear, W.H. Allen & Co, 1845. View/download full book for free at Google books.
- On the structure of the Hindustani language, The Asiatic journal and monthly register for British India, 1828. Read at Google books. Excerpt: "Like the English, which was brought into its present state under similar circumstances (the Norman conquest, and the consequent introduction of the French language into Britain), the Hindustani seems to admit words ad libitum from other languages."
- Why Hindi-Urdu is one language and Arabic is several, Heather Carreiro, 2010. Read at MatadorAbroad. Excerpt: "I could understand Hindi speakers, and they could understand me. Most people in India asked me where I had learned Hindi, and when I responded that I had studied Urdu in Pakistan they were surprised."
- Hindustani as an anxiety between Hindi-Urdu commitment: Linguistic engineering of language loyalty, Dr. S.I. Hasnain and Dr. K.S. Rajyashree, 2003. Read at Language in India. Excerpt: "Both Urdu and Hindi-wallahs feel "paranoid and dispossessed". A sort of a closure and blindness prevails with regard to the matter of Hindi and Urdu and any space for public discourse has been largely appropriated by the protagonists of both Urdu and Hindi."