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".

1983年初，我偶然看到A.考夫曼的书《模糊集理论导论》（学术出版社，纽约，1975年）。这是我对模糊集理论的第一次了解。然后我尝试在这些集合的定义中引入一个新的组件（它决定了非成员的程度），并研究这样定义的新对象的属性。在新的集合中，我将普通运算定义为“n”、“U”、“+”和“.”，但从1983年4月起，我开始更认真地研究它们，当时我定义了类似于“必然性”和“可能性”的模态运算符的运算符。