An initial version of ADS, with a database consisting of 40 papers, was created as a proof of concept in 1988, and the ADS database was successfully connected with the SIMBAD database in the summer of 1993. The creators believed this was the first use of the Internet to allow simultaneous querying of transatlantic scientific databases. Until 1994, the service was available via proprietary network software, but it was transferred to the nascent World Wide Web early that year. The number of users of the service quadrupled in the five weeks following the introduction of the ADS web-based service.