9Solomon W Golomb, Leonard D Baumert. Backtrack program- ming [J]. Journal of the ACM, 1965,12(4):516-524.
10Martin Richards. Backtracking Algorithms in MCPL Using Bit Patterns and Recursion[R]. UCAM-CL-TR433. Unit- ed Kingdom:University of Cambridge, Computer Laborato- ry, 1997.