@inproceedings{h.1927on,
title={On the representation of numbers in the form$ax$^{2}+$by$^{2}+$cz$^{2}+$dt$^{2}},
author={H. D. Kloosterman},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203047361480398},
booktitle={Acta Mathematica},
volume={49},
number={3},
pages={407-464},
year={1927},
}
H. D. Kloosterman. On the representation of numbers in the form$ax$^{2}+$by$^{2}+$cz$^{2}+$dt$^{2}. 1927. Vol. 49. In Acta Mathematica. pp.407-464. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203047361480398.