Petteri Kaski, Patric R. J. Östergård. There exists no symmetric configuration with 33 points and line size 6. Australasian J. Combinatorics, 38:273-278, 2007. [doi]
@article{KaskiO07,
title = {There exists no symmetric configuration with 33 points and line size 6},
author = {Petteri Kaski and Patric R. J. Östergård},
year = {2007},
url = {http://ajc.maths.uq.edu.au/pdf/38/ajc_v38_p273.pdf},
researchr = {https://researchr.org/publication/KaskiO07},
cites = {0},
citedby = {0},
journal = {Australasian J. Combinatorics},
volume = {38},
pages = {273-278},
}