TY - JOUR AU - L. Rosenberg BT - Physical Review A DA - Jan-08-1986 DO - 10.1103/PhysRevA.34.978 PY - 1986 SP - 978 EP - 985 T2 - Physical Review A TI - Gauge-invariant approximations for scattering in a strong external field UR - http://link.aps.org/doi/10.1103/PhysRevA.34.978 VL - 34 SN - 0556-2791 ER -