TY - JOUR A1 - Smith, L. A1 - Hyndman, R.J. A1 - Wood, S.N. T1 - Spline interpolation for demographic variables: The monotonicity problem Y1 - 2004 DO - 10.1007/BF03032212 JF - Journal of Population Research VL - 21 IS - 1 SP - 95 EP - -98 ER -