@article{karatsuba,
    author = {Karatsuba, A. and Ofman, Yu.},
    title = {Multiplication of many-digital numbers by automatic computers},
    journal = {Dokl. Akad. Nauk SSSR},
    year = {1962},
    volume = {145},
    issue = {2},
    pages = {293--294},
    note = {\url{http://mi.mathnet.ru/dan26729}},
}
@InProceedings{rbt,
    author ={Tobias Nipkow},
    title ={Verified Root-Balanced Trees},
    booktitle ={Asian Symposium on Programming Languages and Systems, APLAS 2017},
    pages ={255--272},
    series ={LNCS},
    year ={2017},
    volume ={10695},
    editor ={Bor-Yuh Evan Chang},
    publisher ={Springer},
    note = {\url{https://www21.in.tum.de/~nipkow/pubs/aplas17.pdf}},
}
