@article{eprints705,
          author = {Rachele Foschi and Fabio Spizzichino},
       publisher = {	Seccio de Matematiques i Informatica, E.T.S. d'Arquitectura, Universitat Politecnica},
         journal = {Mathware \& Soft Computing},
            year = {2008},
           title = {Semigroups of Semi-copulas and Evolution of Dependence at Increase of Age},
           pages = {95--111},
          number = {1},
          volume = {15},
             url = {http://eprints.imtlucca.it/705/},
        abstract = {We consider a pair of exchangeable lifetimes X, Y and the families of the conditional survival functions F t (x, y) of
(X ? t, Y ? t) given (X {\ensuremath{>}} t, Y {\ensuremath{>}} t). We analyze some properties of dependence and of ageing for F t (x, y) and
some relations among them}
}