# References for non-zero boundary value problem

I studied linear elliptic, parabolic and hyperbolic PDEs (boundary/initial value problem) in terms of existence, uniqueness and regularity. I studied always, following Evans book "PDE", the case with zero boundary value. I've tried to repeat some energy estimates with non zero boundary value and I got some results that i wanna check. Where could I find references for this kind of problems?

Thanks for the help, Marco Menale