Reference works are an important source for concept definitions, overview articles, and short bibliographies. The Penn Libraries continues to acquire print and online reference works. These are accessible thorugh Franklin Catalog.
Search example: subject:leadership AND (handbook* OR encyclopedia* OR dictionar*)
Also, see the literature-review journals on this guide's "Literature Reviews" tab.
Gale Directory Library - Includes these Gale Reference Directories (select within the search interface)
For Statistical Sources, see these additional guides:
Foundation Directory - provides current, accurate, and comprehensive information on U.S. grantmakers and their grants, drawn from reliable sources, including IRS Form 990s, grantmaker web sites and annual reports, and the grantmakers themselves.
GuideStar - Organization’s full address and contact information, Up to three years of Forms 990, Revenue and expense data for the current fiscal year, CEO, Board Chair, and Board of Directors information.
Grants.gov - Searchable database of funding opportunities available through federal grant-making agencies. Records include program scope, eligibility requirements, deadlines, and program director contact information.
National Science Foundation - Awards Search
National Endowment for the Humanities - Funded Projects Query Form
National Institutes of Health - Research Portfolio Online Reporting Tools
Encyclopedia and dictionaries are great places to start research. Dictionaries will provide clear definitions and descriptions of a term or topic. A good encyclopedia article will outline major research theories and issues, and it describe consensus, controversy, and research fronts; it should also list important, classic, or controversial works that treat the article's topic.
Handbooks are edited works, gathering chapters around a topic. A good handbook chapter will be journal article-length or longer, it will be more discursive than an encyclopedia article, and it will offer a rich bibliography for further reading.