1. Coordinating Geographic Data Acquisition and Access: The National Spatial Data Infrastructure (Executive Order 12906)http://www.fgdc.gov/policyandplanning/executive_order
2. Framework Introduction and Guidehttp://www.fgdc.gov/framework/frameworkintroguide
3. The Geographic Information Framework Data Standardhttp://www.fgdc.gov/standards/projects/FGDC-standardsprojects/framework-data-standard/framework-data-standard
4. OpenGIS Geography Markup Language (GML) Encoding Standardshttp://www.opengeospatial.org/standards/gml
5. An overview of the use of GML in modern spatial data infrastructures;Skoks;Scientific Journal of Riga Technical University Computer Science,2011