Tillotson and Nielsen (1984) made a useful contribution by emphasizing that the method of 'functional normalization' is unrelated to similarity principles, and scale factors obtained from the use of the method are not physically based. They illustrate a simplified version of the method by applying it to analysis of data on microbial CO2 production in soils. They used 'inspectional analysis' together with actual analytical solution of system equations. They solved a non-dimensionalized first order partial differential equation describing diffusion of CO2 within a soil matrix of depth l with a uniformly distributed source term representing microbial CO2 production.