Arnold R. (2005) R&D and Productivity Growth: A Background Paper. Congressional Budget Office.
Bosq D. (1998) Nonparametric Statistics for Stochastic Processes: Estimation and Prediction. Springer-Verlag.
Cai Z., Fan J., & Yao Q.W. (2000) Functional-coefficient regression models for nonlinear time series. Journal of the American Statistical Association 95, 941–956.
Chen R. & Tsay R.S. (1993a) Nonlinear additive ARX models. Journal of the American Statistical Association 88, 955–967.
Chen R. & Tsay R.S. (1993b) Functional-coefficient autoregressive models. Journal of the American Statistical Association 88, 298–308.
Cobb C.W. & Douglas P.H. (1928) A theory of production. American Economic Review 18, 139–165.
de Boor C. (2001) A Practical Guide to Splines. Springer-Verlag.
Hastie T.J. & Tibshirani R.J. (1990) Generalized Additive Models. Chapman and Hall.
Hastie T.J. & Tibshirani R.J. (1993) Varying-coefficient models. Journal of the Royal Statistical Society Series B 55, 757–796.
Hengartner N.W. & Sperlich S. (2005) Rate optimal estimation with the integration method in the presence of many covariates. Journal of Multivariate Analysis 95, 246–272.
Horowitz J. & Mammen E. (2004) Nonparametric estimation of an additive model with a link function. Annals of Statistics 32, 2412–2443.
Huang J.Z. (1998a) Projection estimation in multiple regression with application to functional ANOVA models. Annals of Statistics 26, 242–272.
Huang J.Z. (1998b) Functional ANOVA models for generalized regression. Journal of Multivariate Analysis 67, 49–71.
Huang J.Z. & Shen H. (2004) Functional coefficient regression models for non-linear time series: A polynomial spline approach. Scandinavian Journal of Statistics 31, 515–534.
Huang J.Z., Wu C.O., & Zhou L. (2002) Varying-coefficient models and basis function approximations for the analysis of repeated measurements. Biometrika 89, 111–128.
Huang J.Z. & Yang L. (2004) Identification of nonlinear additive autoregressive models. Journal of the Royal Statistical Society Series B 66, 463–477.
Li Q. & Racine J.S. (2007) Nonparametric Econometrics: Theory and Practice. Princeton University Press.
Linton O.B. (1997) Efficient estimation of additive nonparametric regression models. Biometrika 84, 469–473.
Mammen E., Linton O.B., & Nielsen J.P. (1999) The existence and asymptotic properties of a backfitting projection algorithm under weak conditions. Annals of Statistics 27, 1443–1490.
Nielsen J.P. & Sperlich S. (2005) Smooth backfitting in practice. Journal of the Royal Statistical Society Series B 67, 43–61.
Rodríguez-Póo J.M., Sperlich S., & Vieu P. (2003) Semiparametric estimation of separable models with possibly limited dependent variables. Econometric Theory 19, 1008–1039.
Solow R.M. (1957) Technical change and the aggregate production function. The Review of Economics and Statistics 39, 312–320.
Sperlich S., Tjøstheim D., & Yang L. (2002) Nonparametric estimation and testing of interaction in additive models. Econometric Theory 18, 197–251.
Stone C. J. (1985) Additive regression and other nonparametric models. Annals of Statistics 13, 689–705.
Tokic D. (2003) How efficient were R&D and advertising investments for internet firms before the bubble burst? A DEA approach. Credit and Financial Management Review 9, 39–51.
Wang L. & Yang L. (2007) Spline-backfitted kernel smoothing of nonlinear additive autoregression model. Annals of Statistics 35, 2474–2503.
Xue L. & Yang L. (2006a) Estimation of semiparametric additive coefficient model. Journal of Statistical Planning and Inference 136, 2506–2534.
Xue L. & Yang L. (2006b) Additive coefficient modelling via polynomial spline. Statistica Sinica 16, 1423–1446.
Yang L., Härdle W., & Nielsen J.P. (1999) Nonparametric autoregression with multiplicative volatility and additive mean. Journal of Time Series Analysis 20, 579–604.
Yang L., Park B.U., Xue L., & Härdle W. (2006) Estimation and testing of varying coefficients in additive models with marginal integration. Journal of the American Statistical Association 101, 1212–1227.
Yang L., Sperlich S., & Härdle W. (2003) Derivative estimation and testing in generalized additive models. Journal of Statistical Planning and Inference 115, 521–542.