Louis Hodes. The Logical Complexity of Geometric Properties in the Plane. Journal of the ACM, 17(2):339-347, 1970. [doi]
@article{Hodes70, title = {The Logical Complexity of Geometric Properties in the Plane}, author = {Louis Hodes}, year = {1970}, doi = {10.1145/321574.321587}, url = {http://doi.acm.org/10.1145/321574.321587}, researchr = {https://researchr.org/publication/Hodes70}, cites = {0}, citedby = {0}, journal = {Journal of the ACM}, volume = {17}, number = {2}, pages = {339-347}, }