Need help with Exclusion Ratio in Taxation on Annuities (LIC)

I have an annuity policy with the Life Insurance Corp of India. This was purchased many years back with my post-tax income. I am already receiving the annuity periodically. All these years, I was treating this as fully taxable income when filing my tax returns. Recently I have come across articles about Exclusion Ratio in relation to taxation of annuities, e.g. see the CAclubIndia article  Annuity Taxation.

I have tried finding out the exclsion ratio and also contacted LIC, but have drawn a blank so far.  The people I contacted seem to be unaware of such a term.

My questions:

1. Any guidance on how to find out the exclusion ratio for my LIC annuity policy? Does any one have any experience (success) in this regard?
2. Where (in which section) in the incometax act will I be able to find the mention of excluion ratio in relation to taxation of annuities?

Thanks