On the rotation number of a normal curve
Compositio Mathematica, Tome 13 (1956-1958), pp. 270-276. 
@article{CM_1956-1958__13__270_0,
     author = {Griffin, Jr, John S.},
     title = {On the rotation number of a normal curve},
     journal = {Compositio Mathematica},
     pages = {270--276},
     publisher = {Kraus Reprint},
     volume = {13},
     year = {1956-1958},
     mrnumber = {117717},
     zbl = {0090.13105},
     language = {en},
     url = {http://www.numdam.org/item/CM_1956-1958__13__270_0/}
}
TY  - JOUR
AU  - Griffin, Jr, John S.
TI  - On the rotation number of a normal curve
JO  - Compositio Mathematica
PY  - 1956-1958
SP  - 270
EP  - 276
VL  - 13
PB  - Kraus Reprint
UR  - http://www.numdam.org/item/CM_1956-1958__13__270_0/
LA  - en
ID  - CM_1956-1958__13__270_0
ER  - 
%0 Journal Article
%A Griffin, Jr, John S.
%T On the rotation number of a normal curve
%J Compositio Mathematica
%D 1956-1958
%P 270-276
%V 13
%I Kraus Reprint
%U http://www.numdam.org/item/CM_1956-1958__13__270_0/
%G en
%F CM_1956-1958__13__270_0
Griffin, Jr, John S. On the rotation number of a normal curve. Compositio Mathematica, Tome 13 (1956-1958), pp. 270-276. http://www.numdam.org/item/CM_1956-1958__13__270_0/

H. Hopf, [1] Über die Drehung der Tangenten und Sehnen ebener Kurven. Compositio Math. 2 (1935), pp. 50-62. | JFM | Numdam | Zbl

H. Whitney, [2] On regular closed curves in the plane. Compositio Math. 4 (1937), pp. 276-284. | JFM | Numdam | Zbl