Liên quan Ordovic muộn Ordovic giữa Ordovic sớm Ordovician Ordos (thành phố) Ordos Ordonnaz Ordobrevia amamiensis Ordona Orlovsky (huyện của Orel)
Tài liệu tham khảo WikiPedia: Ordovic_sớm http://palstrat.uni-graz.at/Stratigraphische_Tabel... http://www.gfz-potsdam.de/pb3/pb33/highlights/down... http://norges.uio.no/timescale/Fig11.2_Ord-colB.pd... http://www.stratigraphy.org/camord.htm http://www.stratigraphy.org/floian.htm http://www.stratigraphy.org/geowhen/index.html //tools.wmflabs.org/geohack/geohack.php?language=v... //tools.wmflabs.org/geohack/geohack.php?language=v... //www.worldcat.org/search?fq=x0:jrnl&q=n2:0024-116... //www.worldcat.org/search?fq=x0:jrnl&q=n2:0705-379...
