@article{ZNSL_1992_199_a3,
     author = {R. F. Bikbaev},
     title = {Integrable boundary-value problems and nonlinear {Fourier} harmonics},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {43--50},
     publisher = {mathdoc},
     volume = {199},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1992_199_a3/}
}