Modified Bessel functions: Variants of Bessel functions adapted for scenarios involving exponential growth or decay, commonly appearing in heat conduction and wave propagation models.

D. E. Amos, Computation of Modified Bessel Functions and Their Ratios, Mathematics of Computation, Vol. 28, No. 125 (Jan., 1974), pp. 239-251 ...

Walter Gautschi, Josef Slavik, On the Computation of Modified Bessel Function Ratios, Mathematics of Computation, Vol. 32, No. 143 (Jul., 1978), pp. 865-875 ...