Reference works are an excellent first stop in your research and are incredibly useful for the following:
Reference works are a good starting off point, but should not be cited in your research as they are not considered primary or secondary sources. The only exception is when reference works contain primary and secondary sources (like collections of documents and essays).
Handbooks are similar to encyclopedias but more focused on a specific area, and each 'executive summary' is chapter length with more in-depth coverage of the field. Handbooks typically have 5-10 pages of citations at the end of the summary. To find additional handbooks try a search in the Portland State Library catalog, using "handbook" and your topic keyword.