Dad's Death Certificate not available - Please advise

[Raj_2001_2001]

I am filling out N-400 for my mom, I see Marriage and Death Certificate of my dad is need for mom's application. My Dad passed away 32 years ago in a small town in India. We tried to get a copy of death certificate from local office but they don't have old records. Please advise what are acceptable documents for,

1. Marriage Certificate
2. Death Certificate

Please advise, thanks in advance.