Operations with sparse matrices

Dear mechanicians,

I'am a phd researcher on the field of
computational mechanics. I want to solve a linear system of equations [A]
{x} = {b} with PCG method. With the help of a very illuminating
book "Iterative Methods for Sparse Linear Systems" by Yousef Saad, I manage to
write an algorithm in Fortran90 language. But i have one problem... I
store A matrix in symmetric skyline format (upper triangular). I
searched into BLASSM folder of the SPARKIT2 software, but
I found only amux surboutine to perform a matrix-vector
multiplication in case of A is stored in CSR format. Is there any subroutine for this multiplication [A] {x} when [A] matrix is
stored in symmetric skyline format (upper triangular)?

Thank you in advance!
Marios