Perhaps you should try some spelling variations:
multilayered research » multifaceted research, multilevel research, multilayered reservoir
multilevel hierarchy » multilevel hierarchical
multiple reservoir » multiple reservoirs, multipole reservoir, multi reservoir

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: ((((multiple reservoir) OR (multilevel hierarchy))) OR (multilayered research)).
• Adding a wildcard symbol may retrieve word variants: ((((multiple reservoir) or (multilevel hierarchy))) or (multilayered research))*.