A few key references that were very important in this project are:
The paper by Raffennetti on design and optimization of even-tempered STO basis sets [Raffenetti, 1973]. The paper by Del Chong describes completeness profiles as a visual tool in estimating the completeness of a basis set [Chong, 1995]. Finally, Zeiss and coworkers [Zeiss, 1979] describe field-induced polarization functions for STOs. These are useful for defining basis sets with diffuse functions for (hyper)polarizability and other property calculations.
The procedure for the usage and optimization of fit functions is described by Baerends et al. [Baerends, 1973].
More recent references:
E. van Lenthe and E.J. Baerends, Optimized Slater-type basis sets for the elements 1-118. Journal of Computational Chemistry 24, 1142 (2003)
D.P. Chong, E. van Lenthe, S.J.A. van Gisbergen and E.J. Baerends, Even-tempered Slater-Type orbitals revisited: From Hydrogen to Krypton. Journal of Computational Chemistry 25, 1030 (2004)
D.P. Chong, Augmenting basis set for time-dependent density functional theory calculation of excitation energies: Slater-type orbitals for hydrogen to krypton. Molecular Physics 103, 749 (2005)