Felton, W. L. and McCloy, K. R. 1992. Spot spraying. Agricultural Engineering. 11: 9-12

 Hang, Z., Yubin, L.,Wenfu, W. , Clin, H. , Yanbo, H.,  Xinyu,X. , Liang, J. and Fritz, B. 2010.  Development of a PWM Precision Spraying Controller for Unmanned Aerial Vehicles. Journal of Bionic Engineering 7(2010), 276–283.

Llorens, J., Gil, E., Llop, J. and Escolà, A. 2010.  Variable rate dosing in precision viticulture: use of electronic devices to improve application efficiency. Crop Protection 29(3).

Liu, H. Zhu, H. Shen, Y. Chen, Y. and H. Ozkan, H.E. 2014.  Development of Digital Flow Control System for Multi-Channel Variable-Rate Sprayers. Transactions of the ASABE 57(1): 273-281.

Marshall, E. J. P. 1988. Field-scale estimates of grass weed populations in arable land. Weed Research. 28: 191-198.

Rizzardi, K. 2006. Site-specific weed management in peanut. (ARACHIS HYPOGAEA L. pp.123).

Tangwongkit, R. ,Salokhe, V. ,Jayasuriya, H. 2006.  Development of a real-time, variable rate herbicide applicator using machine vision for between-row weeding of sugarcane fields. Agricultural Engineering International: The CIGR EJournal.

Zaman, Q.U., Esau, T.J., Schumann, A.W., Percival, D.C., Chang Y.K. and Read S.M. 2011. Development of prototype automated variable rate sprayer for real-time spot-application of agrochemicals in wild blueberry fields. Computers and electronics in agriculture. 76(2):175-82.