Perhaps you should try some spelling variations:
communication conservation » communication conversation, communication cooperation, communication preservation
conservation periodicals » communication periodicals
perfusion based » permission based, fusion based, diffusion based
persian based » hessian based, person based, durian based

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: communication conservation periodicals ((persian based) OR (perfusion based)) linear~.
• Adding a wildcard symbol may retrieve word variants: communication conservation periodicals ((persian based) or (perfusion based)) linear*.