From the project website (accessed 2016-07-04):
This publication systematically describes ancient-world information resources on the world-wide web. The bibliographic data presented herein has been programmatically extracted from the content of AWOL - The Ancient World Online (ISSN 2156-2253) and formatted in accordance with a structured data model. We extract information from AWOL about both top-level and subordinate resources. Subordinate resources are those we deduce to be "part of" another resource (e.g., a single issue of a journal or a sub-section of a website). Top-level resources are the opposite: those resources described by AWOL for which we have detected no containing/superior resource.