@article{Smith2004,
author = {Smith, L. and Hyndman, R.J. and Wood, S.N.},
title= {Spline interpolation for demographic variables: The monotonicity problem},
year = {2004},
doi = {10.1007/BF03032212},
journal = {Journal of Population Research},
volume = {21},
number = {1},
pages = {95--98},
}