The generalized effect algebra was presented as a generalization of effect algebra for an algebraic description of the structure of the set of all positive linear operators densely defined on Hilbert space with the usual sum of operators. A structure of the set of not only positive linear operators can be described with the notion of weakly ordered partial commutative group (wop-group). With a restriction of the usual sum, the important subset of all self-adjoint operators forms a substructure of the set of all linear operators. We investigate the properties of intervals in wop-groups of linear operators and showing that they can be organised into effect algebras with nonempty set of states.
