TY - JOUR AU - K. Pohlmeyer TI - Higher order perturbation theory of exponential Lagrangians: fourth order JO - Trudy Matematicheskogo Instituta imeni V.A. Steklova PY - 1975 SP - 201 EP - 205 VL - 135 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/TM_1975_135_a22/ LA - en ID - TM_1975_135_a22 ER -