@article{PismaZhETF.21.278,
    title = {Exchange interaction in exciton excited S states},
    author = {Agekyan, V. T. and Stepanov, Yu. A.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {21},
    issue = {5},
    pages = {278},
    year = {1975},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_22306.shtml},
}