- 1-enkelt.dk
- Angostura Ltd.
- anthon-thorup.dk
- Bitters – Wikipedia, the free encyclopedia
- Bitters by Brad Thomas Parsons – Book – eBook – Random House
- Bitters Old Men
- Bokers Bitters.co.uk
- Craft Bitters Alliance
- DrinkBoy The Lost Art of Bitters
- En Kelt Bitters (in Danish)
- Fee Brothers – Rochester, NY
- Fernet Branca – Digestivo amaro – Distillerie Fratelli Branca
- Gammel Dansk (link to site in English)
- HAVE, the Averna Bitter USA website… Have a drink, have a good time, have a chance
- Hum Botanical Spirit
- Montenegro Srl
- Peychaud’s Bitters by the Sazerac Company
- Scrappy' s Bitters
- Small Hand Foods | Classic ingredients for pre-prohibition era cocktails
- The Bitter Truth – Cocktail bitters
- The Lost Art of Bitters – an article on Drinkboy
- The stork – Genevas and Liquors – A. of orphan Amsterdam
- Underberg – der natürliche Kräuter-Digestif (link to site in English)
- Vinfirma A/S ANTHON THORUP & SØN (in Danish)
- Von Oosten Bitter (in Danish)
