@inproceedings{p.1969on,
title={On functions orthogonal to invariant subspaces},
author={P. R. Ahern, and D. N. Clark},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203219676184091},
booktitle={Acta Mathematica},
volume={124},
number={1},
pages={191-204},
year={1969},
}