@article{700343,
     title = {Positive and oscillating solutions of equation $\dot{x}(t)=-c(t) x(t-\tau )$
               },
     booktitle = {Equadiff 10},
     series = {GDML\_Books},
     publisher = {Masaryk University},
     address = {Brno},
     year = {2002},
     pages = {129-131},
     url = {http://dml.mathdoc.fr/item/700343}
}

Diblík, Josef. Positive and oscillating solutions of equation $\dot{x}(t)=-c(t) x(t-\tau )$
               , dans Equadiff 10, GDML_Books,  (2002), pp. 129-131. http://gdmltest.u-ga.fr/item/700343/