For more information on the general methods and procedures used for parametric growth curve, see the following references.
L. Crow (1974). "Reliability Analysis for Complex, Repairable Systems", Reliability and Biometry, eds. FF. Proschan and R. Serfling. Society for Industrial and Applied Mathematics. 379−410.
W. Nelson (2003). Recurrent Events Data Analysis for Product Repairs, Disease Recurrences, and Other Applications. ASA-SIAM Series on Statistics and Applied Probability.
S.E. Rigdon and A.P. Basu (2000). Statistical Methods for the Reliability of Repairable Systems. John Wiley & Sons, Inc.