This book is composed of following sections : in the first section , we present the nessary definitions and give a well - rounded treatment of known families of almost difference sets ; in the second section , we discuss the possibility of constructing almost difference sets with 2 , 4 and 6 order cyclotomy classes ; in the third section , we construct two new families of almost difference sets by using cyclotomy modulo pq , where p and q are distinct primes ; in the last section , we discuss the methord to construct almost difference sets with difference sets 然而即使这样，已发现的几乎差集还是很有限。本文由以下四个部分组成：第一部分给出必要的定义和综述；第二部分就2阶、 4阶及6阶分圆类可能构成几乎差集的情形给于讨论；第三部分利用模pq ( p ， q为互异素数)分圆类构造了两类新的几乎差集；第四部分讨论了由差集构造几乎差集的方法。
