@Article{KR74,
  author = 	 { David A. Klarner and Ronald L. Rivest },
  title = 	 { Asymptotic Bounds for the Number of Convex $n$-ominoes },
  journal = 	 { Discrete Mathematics },
  OPTyear = 	 { 1974 },
  OPTmonth =     { March },                   
  date =         { 1974-03 },                  
  volume = 	 { 8 },
  number = 	 { 1 },
  pages = 	 { 31--40 },
  doi =          { 10.1016/0012-365X(74)90107-1 },
  url =          { http://www.sciencedirect.com/science/article/pii/0012365X74901071 },
  abstract =     { 
                  Unit squares having their vertices at integer points in the Cartesian plane are called cells. 
                  A point set equal to a union of $n$ distinct cells which is connected and has no finite cut set 
                  is called an $n$-omino. Two $n$-ominoes are considered the same if one is mapped onto the other by
                  some translation of the plane. An $n$-omino is convex if all cells in a row or column form a 
                  connected strip. Letting $c(n)$ denote the number of different convex $n$-ominoes, 
                  we show that the sequence $((c(n))^{1/n}: n=1,2,\ldots)$ tends to a limit $\gamma$ and 
                  $\gamma=2.309138\ldots .$
                 },
}