2) Heisenberg, Werner. The Columbia Encyclopedia, Sixth Edition. 2001
...One of the founders of the quantum theory, he is best known for his uncertainty principle, or indeterminacy principle, which states that it is impossible to determine...

3) quantum theory. The Columbia Encyclopedia, Sixth Edition. 2001
...Just as the theory of relativity assumes importance in the special situation where very large speeds are involved, so the quantum theory is necessary for the special...