-Eigen vectors are always orthogonal to each other.
document term matrix can be obtained by
d-t = d-f x f-f x (t-f)transpose
where d-f represents eigen vectors of dt*td
t-f is eigen vectors of t-t= transpose(d*t)*(d*t) = term-term co-relation matrix
where f-f conatins eigen values of either t-t or d-d
-Rajasekhar
