Hi. I'm looking for a name of this puzzle:

Rules:

The goal is to distribute Ys into cells such that distribution satisfies the following conditions:

1. There is a bijection between Xs and Ys such that we can pair X with Y only if there lies in neighboring cells (horizontaly or verticaly).

2. Two Ys can't lie into neighboring cells (horizontaly, verticaly or diagonaly).

3. The numbers determined the number of Ys in corresponding row or column.

Does anybody know the name of this puzzle, web site with harder problems than this or any good book, please ?

Thanks.