Hansen, Shute, and Landau examined the usability of an assessment-for-learning system that provides audio-tactile graphics for algebra content (

geometric sequences) for individuals with visual impairments.

They start with real numbers and their basic properties, then turn to equations and inequalities, graphing and solving systems of equations and inequalities, polynomials, factoring polynomials, proportions and rational expressions, writing equations of lines along with functions and variations, radicals and rational exponents, quadratic functions, inequalities, algebra of functions, exponential and logarithmic functions, conic sections and a set of miscellaneous topics such as

geometric sequences. Gustafson and Frisk provide exercises, discussion points, and plenty of interaction along with a web site.