A graph G is well-covered provided each maximal independent set of vertices has the same cardinality. The term sk of the independence sequence (s0, s1, . . . , sÎ±) equals the number of independentâ€¦ (More)

When can a d-dimensional rectangular box R be tiled by translates of two given d-dimensional rectangular bricks B1 and B2? We prove that R can be tiled by translates of B1 and B2 if and only if R canâ€¦ (More)

We introduce sphere of in"uence graphs (SIGs) in the Lâˆž-metric and study their elementary properties. We argue that SIGs de4ned with the Lâˆž-metric are superior to Euclidean SIGs of Toussaint inâ€¦ (More)

A focus of community ecology is the spatial distribution of species assemblages and the interactions among species and abiotic features of the environment. While the ubiquity of species associationsâ€¦ (More)

The p-rank of a design D is the rank of its incidence matrix over a field of characteristic p and is denoted by rankp(D). The p-rank is sometimes used to distinguish among non-isomorphic designs, asâ€¦ (More)

We prove two art gallery theorems in which the guards must guard one another in addition to the galler G of points (the guards) in a simple closed polygon (the art gallery) is a guarded guard setâ€¦ (More)

Let U(n, T) be the set of ail matrices of O's and l's of order n with exactly r 0's. We obtain an upper bound for the permanent of a matrix in U(n, t). For 0 <r < 2n and for nz-2n C r < n2-n weâ€¦ (More)

Ecologically successful algae that colonize natural and artificial substrates in the marine environment have distinct strategies for opportunistic dispersal and settlement. The objective of thisâ€¦ (More)