SERVICES UNDER THE UNION AND THE STATES
Article 346: Official language for communication between one State and another or between a State and the Union
The language for the time being authorised for use in the Union for official purposes shall be the official language for communication between one State and another State and between a State and the Union:
Provided that if two or more States agree that the Hindi language should be the official language for communication between such States, that language may be used for such communication.
About Constitution of India
WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC and to secure to all its citizens: JUSTICE, social, economic and political; LIBERTY of thought, expression, belief, faith and worship; EQUALITY of status and of opportunity; and to promote among them all FRATERNITY assuring the dignity of the individual and the unity and integrity of the Nation; IN OUR CONSTITUENT ASSEMBLY this twenty-sixth day of November, 1949, do HEREBY ADOPT, ENACT AND GIVE TO OURSELVES THIS CONSTITUTION