[1] Simple Feature Access - Part 2: SQL Option | OGC (2017-06-05 12:15:39 +09:00) http://www.opengeospatial.org/standards/sfs

[2] Simple Feature Access - Part 1: Common Architecture | OGC (2017-06-05 12:15:56 +09:00) http://www.opengeospatial.org/standards/sfa

[3] Simple Features - Wikipedia (2017-05-24 12:34:37 +09:00) https://en.wikipedia.org/wiki/Simple_Features