Realizing Higher-Level Gauge Symmetries in String Theory: New Embeddings for String GUTs
(1996)
KINETIC MIXING AND THE SUPERSYMMETRIC GAUGE HIERARCHY
Nucl.Phys.B 492 (1996) 104
REALIZING HIGHER LEVEL GAUGE SYMMETRIES IN STRING THEORY: NEW EMBEDDINGS FOR STRING GUTS
Nucl.Phys.B 479 (1996) 113-172