1. Acharius E (1803) Methodus qua omnes detectos lichens secundum organa catrpomorpha ad genera, species et varietates redigere atque observationibus illustrare tentavit. Ulrich, Stockholm, 394 p
2. Acharius E (1814) Synopsis methodica lichenum. Svanborg et Soc., Lund, pp 1–390
3. Adams DG (2002) Cyanobacteria in symbiosis with hornworts and liverworts. In: Rai AN, Bergman B, Rasmussen U (eds) Cyanobacteria in symbiosis. Kluwer Academic Publishers, The Netherlands, pp 117–135
4. Ahmadjian V (1965) Lichens. Ann Rev Microbiol 19:455–473
5. Ahmadjian V (1993) The lichen symbiosis. John Wiley, New York