@article{RamseyOnAP,
title={On a Problem of Formal Logic},
author={F. Ramsey},
journal={Proceedings of The London Mathematical Society},
pages={264-286}
}

This paper is primarily concerned with a special case of one of the leading problems of mathematical logic, the problem of finding a regular procedure to determine the truth or falsity of any given logical formula*. But in the course of this investigation it is necessary to use certain theorems on combinations which have an independent interest and are most conveniently set out by themselves beforehand.