Answer
Russell and Whitehead were two well-known mathematicians who were building on the work of Dedekind, Cantor, and Frege during Gödel's time. They were interested in the foundations of mathematics and published a three-volume work called Principia Mathematica, which attempted to prove all of mathematics from a few basic axioms. Their work was influential, but it also had some problems, which Gödel was able to point out.