Disclosed examples include accessing a search term from a client device; accessing a first identifier, the first identifier corresponding to a first database proprietor, the first identifier to access first user information corresponding to a user of the client device; accessing a second identifier, the second identifier corresponding to a second database proprietor, the second identifier to access second user information corresponding to the user of the client device; providing the search term, the first identifier, and the second identifier in a message; and transmitting the message to a server.