@inproceedings{william1965the,
title={The interpolation of quadratic norms},
author={William F. Donoghue Jr.},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203212470104038},
booktitle={Acta Mathematica},
volume={118},
number={1},
pages={251-270},
year={1965},
}