1. Allen, J.A., Brown, C.S. and Stohlgren, T.J. (2009). Non-native plant invasions of United States national parks. Biol. Invasions, Vol. 11, Pp.: 2195-2207 https://doi.org/10.1007/s10530-008-9376-1
2. Bridson, D. and Forman, L. (1999). The herbarium handbook. Royle Botanic gardens, Kew. 3rd Edn.
3. Dogra, K.S., Kohli, R.K. and Sood, S.K. (2009a). An assessment and impact of three invasive species in the Shivalik hills of Himachal Pradesh, India Inter. J. Biodiver. Conser., Vol. 11, Pp.: 4-10
4. Dogra, K.S., Kohli, R.K., Sood, S.K. and Dobhal, P.K. (2009b). Impact of Ageratum conyzoides L. the diversity and composition of vegetation in the Shivalik hills of Himachal North-western Himalaya. Inter. J. Biodiver. Conser., Vol. 15, Pp.: 135-145
5. Downey, P.O. and Richardson, D.M. (2016). Alien plant invasions and native plant extinctions: a six-threshold framework. AoB Plants Plw047. Published online https://doi.org/10.1093/aobpla/plw047
6. Gurevitch, J. and Padilla D.K. (2004). Are invasive species a major cause of extinctions? Trends in Ecology and Evolution, Vol. 19, Pp.: 470-474 https://doi.org/10.1016/j.tree.2004.07.005
7. Hulem, E.H., Pysek, P., Pergl, J., Jarosik, V. Schaffner, U. and Vila, M. (2014). Greater Focus Needed on Alien Plant Impacts in Protected Areas. Conservat. Lette., Vol. 7(5). Pp.: 459-466 https://doi.org/10.1111/conl.12061
8. Jaryan, V., Uniyal S.K., Gupta, R.C. and Singh, R.D. (2012). Alien flora of Himalayan State of Himachal Pradesh. Environ. Monit. and Assesm. Vol. 185(7), Pp.: 6129-6153 https://doi.org/10.1007/s10661-012-3013-2
9. Kohli, R.K., Batish, D.R., Singh, H.P. and Dogra, K.S. (2006). Status, invasiveness and environmental threats of three tropical American invasive weeds Parthenium hysterophorus L., Ageratum conyzoides L., Lantana camara L. in India. Biol. Invasions, Vol. (8). Pp.: 1501-1510 https://doi.org/10.1007/s10530-005-5842-1
10. Kohli, R.K., Dogra, K.S., Batish, D.R. and Singh, H.P. (2004). Impact of invasive plants on the structure and composition of natural vegetation of north western Indian Himalayas. Weed Tech., Vol. (18), Pp.: 1296-1300 https://doi.org/10.1614/0890-037X(2004)018[1296:IOIPOT]2.0.CO;2
11. Pickering, C. and Mount, A. (2010). Do tourists disperse weed seed? A global review of unintentional human-mediated terrestrial seed dispersal on clothing, vehicles and horses. J. Sustain Tour., Vol. 18, Pp.: 239-256 https://doi.org/10.1080/09669580903406613
12. Pysek, P., Jarosik, V. and Pergal, J. (2011). Alien Plants Introduced by Different Pathways Differ in Invasion Success: Unintentional Introductions as a Threat to Natural Areas. Plos One, Vol. 6 (9). e24890. Published online https://doi.org/10.1371/journal.pone.0024890
13. Sekar, K.C., Pandey, A., Srivastava, S.K. and Giri, L. (2015). Invasive alien plants of Himachal Pradesh, India. Indian Forester. Vol. 141 (5), Pp.: 520-527