Constantin Corduneanu 
Almost Periodic Oscillations and Waves [PDF ebook] 

Metric Spaces and Related Topics.- Basic Properties of Almost Periodic Functions.- Fourier Analysis of Almost Periodic Functions.- Linear Oscillations.- Almost Periodic Nonlinear Oscillations.- Almost Periodic Waves.

 C. Corduneanu has published extensively:
Integral Equations and Applications, HC, 1991, Cambridge Univ. Press, 978-0521340502, 376 pp.
Functional Equations with Causal Operators (Stability and Control: Theory, Methods and Applications, 16)  (Kindle Edition), $119.95, Taylor & Francis, 2007
Functional Equations with Causal Operators (Stability and Control: Theory, Methods and Applications, 16)  (HC Edition), $119.95, CRC, 2002, 978-0415271868
with I. Sandberg, Volterra Equations and Applications (Stability and Control), $179.00, 512pp, CRC, 2000, 978-9056991715
The author is a renowned expert in the fields of ordinary and partial differential equations.