Peter A. Fejer. 2 Degrees. Math. Log. Q., 35(1):3-14, 1989. [doi]
@article{Fejer89,
title = {2 Degrees},
author = {Peter A. Fejer},
year = {1989},
doi = {10.1002/malq.19890350102},
url = {http://dx.doi.org/10.1002/malq.19890350102},
researchr = {https://researchr.org/publication/Fejer89},
cites = {0},
citedby = {0},
journal = {Math. Log. Q.},
volume = {35},
number = {1},
pages = {3-14},
}