Controlled topical vocabularies (CVs) are built into information systems to aid browsing and retrieval of items that may be unfamiliar, but it is unclear how this feature should be integrated with standard keyword searching. Few systems or scholarly prototypes have attempted this, and none have used the most widely used CV, the Library of Congress Subject Headings (LCSH), which organizes monograph collections in academic libraries throughout the world. This paper describes a working prototype of a Web application that concurrently allows topic exploration using an outline tree view of the LCSH hierarchy and natural language keyword searching of a real-world Science and Engineering bibliographic collection. Pilot testing shows the system is ...