. "http://www.iso.org/iso/catalogue_detail?csnumber=31889"^^ . . "Surface Density"@en . . "http://en.wikipedia.org/wiki/Area_density"^^ . "The area density (also known as areal density, surface density, or superficial density) of a two-dimensional object is calculated as the mass per unit area." . "\\(\\rho_A\\)"^^ . . . . "\\(\\rho_A = \\frac{dm}{dA}\\), where \\(m\\) is mass and \\(A\\) is area."^^ .