## Onesided Magnetized Pentominoes

Here are the 63 pieces packed in nine 5x7 rectangles.

I saw the first solution to this problem getting a mail from
Brendan Owen in October 2001.

My first idea was to make three 3-fold and one 6-fold copy of the pieces.
Unfortunately there are some constraints on this problem and it can be solved
only for the X, I and Z pento.