  The paper studies the set of all square binary matrices containing an exact
number of 1's in each rows and in each column. A connection is established
between the cardinal number of this set and the cardinal number of its subset
of matrices containing 1 in the lower right corner. With the help of this
result a new proof is advanced of the I. Good and J. Grook theorem. In
connection with the firs result a classification has also been made of square
binary matrices containing three 1's in each row and column and 1 in the lower
right corner.
