Stellar Population Models and Individual Element Abundances II: Stellar   Spectra and Integrated Light Models
  The first paper in this series explored the effects of altering the chemical mixture of the stellar population on an element by element basis on stellar evolutionary tracks and isochrones to the end of the red giant branch. This paper extends the discussion by incorporating the fully consistent synthetic stellar spectra with those isochrone models in predicting integrated colors, Lick indices, and synthetic spectra. Older populations display element ratio effects in their spectra at higher amplitude than younger populations. In addition, spectral effects in the photospheres of stars tend to dominate over effects from isochrone temperatures and lifetimes, but, further, the isochrone-based effects that are present tend to fall along the age-metallicity degeneracy vector, while the direct stellar spectral effects usually show considerable orthogonality. 
H.-c. Lee, G. Worthey, A. Dotter, B. Chaboyer, D. Jevremovic, E.   Baron, M. M. Briley, J. W. Ferguson, P. Coelho, S. C. Trager