TY - GEN AU - Piris,M AU - Matxain,J M AU - Lopez,X AU - Ugalde,J M TI - Communication: The role of the positivity N-representability conditions in natural orbital functional theory SN - 1089-7690 PY - 2011///0111 N1 - Publication Type: Journal Article UR - https://doi.org/10.1063/1.3481578 ER -