Google Advanced Search
http://www.google.com/advanced_search
You can use commands to do an Advanced Search in "regular" Google Search.
Sample Search:
filetype: pdf [give me ONLY pdf documents]
why? Most research reports are published online in pdf format.
alternative-- filetype:ppt for powerpoint presentations
domain: org [give me ONLY results from .org web sites]
why? Most research organizations are nonprofits, which use the .org domain.
alternative-- domain:edu for university web sites.
"employee participation" [give me only documents that contain this phrase]
alternative-- whatever Key Words and Key Phrases define your research topic.