Abstract
A subspace lattice L on H is called commutative subspace lattice if all projections in L commute pairwise. It is denoted by CSL. If L is a CSL, then algL is called a CSL algebra. Under the assumption m + n not equal 0 where m; n are fixed integers, if delta is a mapping from L into itself satisfying the condition (m + n)delta(A(2)) = 2m delta(A)A + 2nA delta(A) for all A is an element of A, we call delta an (m, n) Jordan derivation. We show that if delta is a norm continuous linear (m, n) mapping from A into it self then delta is a (m, n)-Jordan derivation.