After you have consulted books and journal articles, you may also want to use web resources. Take a look at Evaluating Resources to help you evalute the websites you find. Look for websites that include primary/historical sources, are part of a scholarly project, or indicate an author or sponsoring institution.  These sites contain reliable information:

• American Society for Theatre Research
• American Theatre Magazine
• Asian American Performers Action Coalition
• Association for Hispanic Classical Theater
• Consortium of Asian-American Theaters and Artists
• Costume Institute @ The Metropolitan Museum of Art
• Didasakalia (open-access peer-reviewed journal)
• The Federal Theatre Project, 1935-1939 (Library of Congress)
• Howlround: Latinx Theatre Commons
• Internet Broadway Database (IBDB)
• Latino Theatre Company at The Los Angeles Theatre Center
• London Theatre Guide
• National Theatre (London)
• New York Public Library for the Performing Arts
• North Carolina Black Repertory Company/National Black Theatre Festival
• Ping Chong+Company
• Playbill Magazine
• Records of Early English Drama (REED) Centre for Research in Early English Drama
• Royal Court Theatre
• Royal Shakespeare Company Image Collection
• Shakespeare in the "Post"Colonies
• Shakespeare's Globe Theatre
• Society of London Theatre
• Theater and Amphitheater in the Roman World
• Tony Awards
• York Mystery Plays