Sambucus nigra - Description of the Elder and photographs of flowers, leaves, berries and an off-the-ground tree. - http://www.plant-identification.co.uk/skye/caprifoliaceae/sambucus-nigra.htm
Sambucus racemosa ssp. pubens - Information on distribution and occurrence, value and use, characteristics, and fire ecology. - http://www.fs.fed.us/database/feis/plants/shrub/samracp/
Sambucus cerulea - Information on distribution and occurrence, value and use, characteristics, and fire ecology. - http://www.fs.fed.us/database/feis/plants/shrub/samcer/