1. Basic calculus on time scales and some of its applications;Agarwal;Results Math.,1999
2. R.P. Agarwal, D. O'Regan, P.J.Y. Wong, Positive Solutions of Differential, Difference and Integral Equations, Kluwer Academic Publishers, Dordrecht, 1999.
3. B. Aulbach, S. Hilgar, Linear dynamic processes with inhomogeneous time scale, Nonlinear Dynamics and Quantum Dynamical Systems, Akademie Verlag, Berlin, 1990.
4. Green's functions and comparison theorems for differential equations on measure chains, Dynamics Continuous;Erbe;Discrete Impulsive Systems,1999
5. L.H. Erbe, A. Peterson, Positive solutions for a nonlinear differential equation on a measure chain, Mathematical and Computer Modelling.