@article{PismaZhETF.51.604,
    title = {Gupta-Bleuler operator quantization in superstring theory},
    author = {Demichev, A. P. and Iofa, M. Z.},
    journal = {Письма в ЖЭТФ},
    volume = {51},
    issue = {12},
    pages = {604},
    year = {1990},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_17693.shtml},
}