Russell and Alfred North Whitehead(1861-1974) in 1903 proposed an axiomatic theory of sets in their three-volume work called Principia Mathematicians found it awkward to use. An axiomatic set theory which is workable and is fully logistic was given in 1908 by Ernst Zermello(1871-1953). This wa improved in 1921 by Abraham A. fraenkel (1891-1965) and T. Skolem (1887-1963) and is now known as 'Zermello-frankel(ZF)-axiomatic theory of sets.