Construction of nested orthogonal arrays

A (symmetric) nested orthogonal array is a symmetric orthogonal array O A ( N , k , s , g ) which contains an O A ( M , k , r , g ) as a subarray, where M < N and r < s . In this communication, some methods of construction of nested symmetric orthogonal arrays are given. Asymmetric nested orthogonal arrays are defined and a few methods of their construction are described.