Legal provisions for optional referendums at national level

India's Constitution of 1949 withAmendments through 2012

https://??www.??constituteproject.??org/??constitution/??India_??2012.??pdf

Direct Democracy in Asia: A Reference Guide to the Legislation and Practice (2005), page 124 on India.

http://??www.??docstoc.??com/??docs/??74258274/??Direct-??Democracy-??in-??Asia

http://??eci.??nic.??in/??eci_??main/??recent/??21-??7-??12%20??editorial.??pdf