Note on the two congruences $a{x}^{2}+b{y}^{2}+e\equiv 0$, $a{x}^{2}+b{y}^{2}+c{z}^{2}+d{w}^{2}\equiv 0\phantom{\rule{0.222222em}{0ex}}\left(\text{mod.}\phantom{\rule{4pt}{0ex}}p\right)$, where $p$ is an odd prime and $a¬\equiv 0$, $b¬\equiv 0$, $c¬\equiv 0$, $d¬\equiv 0\phantom{\rule{0.222222em}{0ex}}\left(\text{mod.}\phantom{\rule{4pt}{0ex}}p\right)$
Rendiconti del Seminario Matematico della Università di Padova, Volume 18 (1949), p. 311-315
@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},
publisher = {Seminario Matematico of the University of Padua},
volume = {18},
year = {1949},
pages = {311-315},
zbl = {0033.01202},
language = {en},
url = {http://www.numdam.org/item/RSMUP_1949__18__311_0}
}

Bagchi, Haridas. 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 $a \lnot \equiv 0$, $b \lnot \equiv 0$, $c \lnot \equiv 0$, $d \lnot \equiv 0 \: (\text{mod. } p)$. Rendiconti del Seminario Matematico della Università di Padova, Volume 18 (1949) pp. 311-315. http://www.numdam.org/item/RSMUP_1949__18__311_0/`