Von Mises
The sub-sequence selection criterion imposed by von Mises is important, because although 0101010101... is not biased, by selecting the odd positions, we get 000000... which is not random. Von Mises never totally formalized his definition of a proper selection rule for sub-sequences, but in 1940 Alonzo Church defined it as any recursive function which having read the first N elements of the sequence decides if it wants to select element number "N" + 1. Church was a pioneer in the field of computable functions, and the definition he made relied on the Church Turing Thesis for computability. This definition is often called "Mises–Church randomness".