capt.topgun
I see from your profile that you are working as a B737 Captain in India.
It should be fairly easy to acquire, by fair means or foul, a copy of Air India's or Indian Airlines' performance handbook for pilots.
They're both quite straight-forward and give good explanations in easy language.
I'll even admit to having sneaked a few paragraphs here and there (I think the word is plagiarised) for inclusion in manuals I've prepared for my own company.
Where've you been? Haven't heard from you in ages.
Smokey