T numbers also comprise a set of measure 0. It took about 35 years to show their existence. Wolfgang M. Schmidt in 1968 showed that examples exist. However, almost all complex numbers are S numbers. Mahler proved that the exponential function sends all non-zero algebraic numbers to S numbers: this shows that "e" is an S number and gives a proof of the transcendence of . This number is known not to be a U number. Many other transcendental numbers remain unclassified.