We correct an error in [1]. There is an error in the proof of Theorem 2.1, which was pointed out to me by K. Szczypkowski. On page 101, line 18, although A(n) backslash L-n subset of boolean OR(n)(i=1)(A(i) backslash K-i), the assertion concerning the projections is not necessarily true. The following should replace the proof of Theorem 2.1, from line 6 of page 101 through the line that is 7 lines before the end of page 101.