@article{TM_1975_135_a22,
     author = {K. Pohlmeyer},
     title = {Higher order perturbation theory of exponential {Lagrangians:} fourth order},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {201--205},
     publisher = {mathdoc},
     volume = {135},
     year = {1975},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TM_1975_135_a22/}
}