ISI maths.

[Economics student]

I am form commerce with maths background, but i have a decent background in maths. i have also done maths in my graduation. ISI maths section still scares me. Can you tell which AIEEE/IIT sort of book should I refer, to make sure I get a hand of solving those type of questions. 2013 sample paper is still easier, others are more than scary.
Please help!