  The 0-1 matrix A contains a 0-1 matrix M if some submatrix of A can be
transformed into M by changing some ones to zeroes. If A does not contain M,
then A avoids M. Let ex(n,M) be the maximum number of ones in an n x n 0-1
matrix that avoids M, and let ex_k(m,M) be the maximum number of columns in a
0-1 matrix with m rows that avoids M and has at least k ones in every column. A
method for bounding ex(n,M) by using bounds on the maximum number of edges in
bar visibility graphs was introduced in (R. Fulek, Discrete Mathematics 309,
2009). By using a similar method with bar visibility hypergraphs, we obtain
linear bounds on the extremal functions of other forbidden 0-1 matrices.
