• Carex opaca (Bicknell's sedge) | USDA PLANTS Database (About This Site)
• Carex opaca | Biota of North America Project (BONAP) (About This Site)
• Carex opaca (F.J.Herm.) P.Rothr. & Reznicek | Plants of the World Online (POWO) (About This Site)
• Carex opaca | Flora of North America (About This Site)