Topological properties of operator generalized effect algebras Lorentzian manifolds having the killing property General formula for symmetry factors of Feynman diagrams On the spectrum of the Schrodinger Hamiltonian of the one-dimensional harmonic oscillator perturbed by two identical attractive point interactions The logic order on a generalized Hermitian algebra The truncation and renormalizability of the superstring and heterotic string effective actions Necessary conditions for optimality of decomposable entanglement witnesses