1. Awasthi, D.D., 2007. A Compendium of the Macrolichens from India, Nepal and Sri Lanka. Bishen Singh Mahendra Pal Singh, Dehradun, India. pp.580
2. Awasthi, G., 1986. Lichen genus Usnea in India. J. Hattori Bot. Lab. 61, pp.333–421
3. Clerc, P., 1987. Systematics of the Usnea fragilescens aggregate and its distribution in Scandinavia. Nord. J. Bot, 7, pp.479–495
4. Clerc P. and Herrera-Campos, M.A., 1997. Saxicolous species of Usnea subgenus Usnea (lichenized Ascomycetes) in North America. Bryologist, 100(3), pp.281– 301
5. Eriksson, O.M., 2005. Outline of Ascomycota. Myconet 11, pp.1–113
6. Halonen P., Clerc P., Goward T., Brodo, I.M., and Wulff, K. (1998). Synopsis of the genus Usnea (lichenized Ascomycetes) in British Columbia, Canada. Bryologist, 101(1), pp.36–60
7. Halonen P., Myllys L., Ahti, T. and Petrova O.V., 1999. The lichen genus Usnea in East Fennoscandia ? III. The shrubby species. Ann. Bot. Fenn. 36, pp.235-256
8. Jaklitsch, W.M., Baral, H.O., Lücking, R. and Lumbsch, H.T., 2016. Ascomycota. In: Frey, W. (ed.) Syllabus of Plant Families – Adolf Engler’s Syllabus der Plafanzenfamilien. Borntraeger, Stuttgart, pp.322
9. Kamal,S., Manish, S., Savita J. and Jasumati 2015. Assessment of Antibacterial Activity of Usnea Species of Shimla Hills. Int. J.Curr.Microbiol.App.Sci. 4(7), pp.413-425
10. Kirk, P. M., Cannon, P. F., Minter, D.W. and Stalpers, J.A., 2008. Dictionary of the fungi, 10th edition. CAB International, Walling ford
11. Mittermeier, R.A., Gil, P.R., Hoffman, Pilgrim, M.J., Brooks, T., Mittermeier, C.G., Lamoreux, J. and de Fonseca G.A.B. (eds.). 2005. Hotspots revisited: Earth’s biologically richest and most endangered terrestrial ecoregions. Mexico: CEMEX. pp.392
12. Motyka, J., 1936–1938. Lichenum generis Usnea studium monographicum. Pars systematica. Vol 1, 2. Leopoli
13. Ohmura, Y., 2001. Taxonomic study of the genus Usnea (lichenized Ascomycetes) in Japan and Taiwan. J. Hattori Bot. Lab. 90, pp. 1-96
14. Ohmura, Y., 2012. A synopsis of the lichen genus Usnea (Parmeliaceae, Ascomycota) in Taiwan. Mem. Natl. Mus. Nat. Sci., Tokyo, 48, pp. 91-137
15. Orange, A., James, P.W. and White, F.J. (2001). Microchemical Methods for the Identification of Lichens. British Lichen Society, London
16. Prateeksha, B., Paliya, S., Bajpai, R., Jadaun,V., Kumar, J., Kumar, S., Upreti, D. K., Singh, B. R., Nayaka,S., Joshi,Y. and Singh, B.N., 2016.The genus Usnea: a potent phytomedicine with multifarious ethnobotany, phytochemistry and pharmacology RSC Adv., 6, pp.21672 – 21696
17. Shukla, P., Upreti, D.K. and Tewari, L.M., 2014. Lichen gemus Usnea (Parmeliaceae, Ascomycota) in Uttarakhand, India. Current Research in Environmental & Applied Mycology, 4(2), pp.188–201 https://doi.org/10.5943/cream/4/2/6
18. Singh, K.P. and Sinha, G.P., 2010. Indian lichens: an annotated checklist. Botanical Survey of India, Kolkata. pp.571
19. Stevens, G.N., 1999. A revision of the lichen family Usneaceae in Australia. Schweizerbart science publishers, Johannesstr. Stuttgart, Germany. pp.1-128
20. Swinscow, T.D.V. and Krog H., 1974. Usnea subgenus Eumitria in East Africa. - Norw. J. Bot. 21, pp.165-185
21. Swinscow, T.D.V. and Krog H., 1975. The Usnea undulata aggregate in East Africa. Lichenologist, 7, pp.121-138
22. Swinscow, T.D.V. and Krog H., 1976a. The Usnea articulata aggregate in East Africa. Norw. J. Bot., 23, pp.261-268
23. Swinscow, T.D.V. and Krog H., 1976b. The Usnea bornmuelleri aggregate in East Africa. Norw. J. Bot., 23, pp.23-31
24. Swinscow, T.D.V. and Krog H., 1978. Pendulous species of Usnea in East Africa. Norw.J. Bot., 25, pp.221-241
25. Swinscow, T.D.V. and Krog H., 1979. The fruticose species of Usnea subgenus Usnea in East Africa. Lichenologist, 11, pp.207-252
26. White, F.J. and James, P.W., 1985. A new guide to the microchemical technique for the identification of lichen substances. British Lichen Society Bulletin, 57, pp.1-41