So-called "grey literature" consists of documents that are not published through traditional commercial channels. Grey literature includes reports, conference papers, dissertations, technical & other trade papers and documents in repositories, as well as working papers and policy documents. The grey literature is extremely useful, especailly n the field of public health, but is very hard to locate.
This page contains some links that might be helpful when searching for grey literature.
Finding the Grey Literature is extremely difficult. A list of various databases that will help you to locate documents is included on this page, but that does not mean that every document will be available. Unfortunately, if there is no full text or PDF link to the document itself, the chances of obtaining this document are very limited.
You could try to contact the authors directly to ask for a copy. If all else fails, you might need to use the abstract only (if one has been provided).