When you are searching the literature consider the different types of information available.  In addition to specifying your topic you can also specify what type of information you want, e.g. historical, landmark, seminal, empirical, or others.  This is not a definitive list.  Other categories of information exist. Use these as models for your searching. 

Historical:

• examining past evidence, events, or progress on a particular subject
• can show patterns that occurred in the past, over time, and solutions
• can add perspective to how we examine current events and educational practices

"Historical" Search Strategies:

• books and articles: combine your topic with history, introduction, review, or overview

Landmark and Seminal:

• pivotal points in the historical development of a research topic
• often responsible for framing a particular question or a research tradition
• may be the original source of key concepts or terminology used in the subsequent literature

"Landmark and Seminal" Search Strategies:

• consult textbooks or subject encyclopedias providing overviews 
• articles will frequently note landmark and seminal work; note the authors you see cited repeatedly; search their names for earlier works too
• books: combine your topic with encyclopedia or introduction

• articles: combine your topic with synonyms like seminal, landmark, classic, groundbreaking

Empirical/Primary:

• a method of gaining knowledge by means of direct and/or indirect observation or experimentation
• empirical research studies support a hypothesis or research question by using empirical evidence, or data that have been collected in the pursuit of knowledge.  Empirical evidence can include qualitative, quantitative or other forms of analysis
• empirical study articles usually have these:  abstract, introduction/literature review, methodology, results, discussion, list of references

"Empirical" Search Strategies:

• books and articles: combine your topic with synonyms such as study, research, empirical, methodology, results, findings, qualitative, or quantitative