On the argument functions of simple closed curves and simple arcs
Compositio Mathematica, Volume 4  (1937), p. 271-275
@article{CM_1937__4__271_0,
author = {Van Kampen, E. R.},
title = {On the argument functions of simple closed curves and simple arcs},
journal = {Compositio Mathematica},
publisher = {Johnson Reprint Corporation},
volume = {4},
year = {1937},
pages = {271-275},
zbl = {0016.13803},
language = {en},
url = {http://www.numdam.org/item/CM_1937__4__271_0}
}

Van Kampen, E. R. On the argument functions of simple closed curves and simple arcs. Compositio Mathematica, Volume 4 (1937) , pp. 271-275. http://www.numdam.org/item/CM_1937__4__271_0/