@inproceedings{gunnar1966minimization,
title={Minimization problems for the functional sup_{$x$}$F(x, f(x), f'(x))$. (II)},
author={Gunnar, and Aronsson},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203436309404059},
booktitle={Arkiv for Matematik},
volume={6},
number={4},
pages={409-431},
year={1966},
}
Gunnar, and Aronsson. Minimization problems for the functional sup_{$x$}$F(x, f(x), f'(x))$. (II). 1966. Vol. 6. In Arkiv for Matematik. pp.409-431. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203436309404059.