In 1994, Donald and Kevin Dahm began using numerical techniques to calculate remission and transmission from samples of varying numbers of plane parallel layers from absorption and remission fractions for a single layer.  Their plan was to "start with a simple model, treat the problem numerically rather than analytically, then look for analytical functions that describe the numerical results. Assuming success with that, the model would be made more complex, allowing more complex analytical expressions to be derived, eventually, leading to an understanding of diffuse reflection at a level that appropriately approximated particulate samples."  They were able to show the fraction of incident light remitted, , and transmitted, , by a sample composed of layers, each absorbing a fraction  and remitting a fraction  of the light incident upon it, could be quantified by an Absorption/Remission function (symbolized  and called the ART function), which is constant for a sample composed of any number of identical layers.