In the beginning of 1983, I came across A. Kaufmann's book "Introduction
to the theory of fuzzy sets" (Academic Press, New York, 1975). This was
my first acquaintance with the fuzzy set theory. Then I tried to
introduce a new component (which determines the degree of
non-membership) in the definition of these sets and to study the
properties of the new objects so defined. I defined ordinary operations
as "n", "U", "+" and "." over the new sets, but I had began to look more
seriously at them since April 1983, when I defined operators analogous
to the modal operators of "necessity" and "possibility". The late George
Gargov (7 April 1947 - 9 November 1996) is the "god- father" of the sets
I introduced - in fact, he has invented the name "intu- itionistic
fuzzy", motivated by the fact that the law of the excluded middle does
not hold for them. Presently, intuitionistic fuzzy sets are an object of
intensive research by scholars and scientists from over ten countries.
This book is the first attempt for a more comprehensive and complete
report on the intuitionistic fuzzy set theory and its more relevant
applications in a variety of diverse fields. In this sense, it has also
a referential character.