.

  Zarco-Tejada, P. J., Miller, J. R., Noland, T. L., Mohammed, G. H., & Sampson, P. H. (2001). Scaling-up and model inversion methods with narrowband optical indices for chlorophyll content estimation in closed forest canopies with hyperspectral data.  IEEE Transactions on Geoscience and Remote Sensing ,  39 (7), 1491-1507. In this paper, the author uses vegetation index as a merit function. The method is more stable than using all channels. Integrating empirical method, physics based model inversion could be improved. 

Daughtry, C.S.T., Walthall, C.L., Kim, M.S., de Colstoun, E.B. and McMurtrey, J.E., 2000. Estimating corn leaf chlorophyll concentration from leaf and canopy reflectance. Remote Sensing of Environment, 74(2): 229-239. Background effects, such as LAI and soil, interfere the leaf signal. Using double indices -ratio of indices sensitive to background to those sensitive to foliar traits - would contribute to reduce redundant signals.

Pu, R., Ge, S., Kelly, N.M. and Gong, P., 2010. Spectral absorption features as indicators of water status in coast live oak ( Quercus agrifolia ) leaves. International Journal of Remote Sensing, 24(9): 1799-1810. Foliar traits can be retrieved by only several absorption feature.