Mathematically precise statement of the unfolding problem

Although numerous papers have appeared on unfolding radiation data and many computer programs have been made and used to solve this important inverse problem, it remains almost an art accompanied by its critics with their opinions and controversy. The reason for this being so is that, surprisingly, no concise, precise mathematical statements of the problems being solved appear in these earlier papers on unfolding. This paper presents what appears to be the first mathematically precise statement of the unfolding problem to be made