@article{RSMUP_1949__18__311_0,
     author = {Bagchi, Haridas},
     title = {Note on the two congruences $ax^2 + by^2 + e \equiv 0$, $ax^2 + by^2 + cz^2 + dw^2 \equiv 0 \: (\text{mod. } p)$, where $p$ is an odd prime and $a \lnot \equiv 0$, $b \lnot \equiv 0$, $c \lnot \equiv 0$, $d \lnot \equiv 0 \: (\text{mod. } p)$},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {311--315},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {18},
     year = {1949},
     zbl = {0033.01202},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_1949__18__311_0/}
}