1. Unsupervised curve clustering using B-splines;Abraham;Scandinavian Journal of Statistics,2003
2. Council Directive ° 30 of 22 April, 1999 relating to limit values for sulphur dioxide (SO2), nitrogen dioxide and oxides of nitrogen (NOX), particulate matter (PM) and lead in ambient air in which emission limits for these pollutants are set.
3. Council Directive ° 62 of 27 September, 1996 on ambient air quality assessment and management.
4. On Polya frequency functions IV: the fundamental splines and their limits.;Curry;Journal d'Analyse Mathématique,1966