Hello,
There was a mistake in the question itself.
No, the small letter a is equal to the big letter A.
Only, the relationship between these two is as follows:
e^{-a(t,T)} = A(t,T). where a(t,T)=A(t,T)
i managed to do it using the fact that phi{1}phi{2} = -2/sigma^(2)
and
phi{1} - phi{2} = 2*gamma/ sigma^(2)
My apology for any inconvenience.