Third parties can submit search requests using Search/Retrieval via URL (SRU), a standard protocol that provides an HTTP REST API for search queries. SRU is the evolution of Z39.50, using HTTP instead of the custom Z39.50 communications protocol.
Emerald's supports SRU version 2.0 and recommends using SRU in place of the legacy Z39.50 service.
Search/Retrieval via URL (SRU)
If you require additional support regarding SRU itself, please contact the Library of Congress in the first instance.