Poset Block Equivalence of Integral Matrices 
	


There is an omission in the statement of the
definition of a matrix in SL_P(n,R) on page 3863 
(paragraph 4 of the Definitions section): 
not only the matrix, but also each of its n
diagonal blocks, should have determinant 1.

The rest of the paper was written for this expanded
definition; the error was that it was not stated
fully. There is no change in the statement of theorems
and proofs elsewhere in the paper.