Polyominoes -- the many different shapes of dominoes having three or more faces -- were introduced to recreational mathematics by Solomon Golomb in 1954. Since then, they have been extensively investigated; many of their mathematical properties are discussed in Golomb's Polyominoes (Scribner's, 1962). Perhaps the most interesting polyominoes are the 12 distinct pentominoes -- all the possible shapes of dominoes having exactly five faces. There are many ways in which the pentominoes can be assembled to form rectangles of size 3 x 20, 4 x 15, 5 x 12 and 6 x 10.
Lindon, J. A.
"A New Pentomino Puzzle,"
Word Ways: Vol. 4
, Article 3.
Available at: http://digitalcommons.butler.edu/wordways/vol4/iss2/3