1. Foundations of Databases;Abiteboul,1995
2. Possible and certain answers for queries over order-incomplete data;Amarilli,2017
3. A query language for list-based complex objects;Colby,1994
4. Concepts for modeling and querying list-structured data;Colby;Inf. Process. Manag.,1994
5. Ordered Sets: An Introduction;Schröder,2003