  We introduce the notion of Gabriel filter for a preadditive category C and we
show that there is a bijective correspondence between Gabriel filters of C and
hereditary torsion theories in the category of additive functors (C,Ab),
obtaining a generelization of the theorem given by Gabriel [Ga] and Maranda
[Ma] which establishes a bijective correspondence between Gabriel filters for a
ring and hereditary torsion theories in the corresponding category of modules.
