How has the description of India as a "Sovereign Democratic Republic" changed over time according to the text?
According to the text, the description of India as a "Sovereign Democratic Republic" has changed over time in the following way:

1. The Constitution (Forty-second Amendment) Act, 1976, substituted "Sovereign Socialist Secular Democratic Republic" for "Sovereign Democratic Republic."
2. The same amendment act also substituted "Unity and integrity of the Nation" for "Unity of the Nation."