1- Ahmed F., Al-Mamun H. A., Bari A. S. M. H., Hossain E., and Kwan P. 2012. Classification of crops and weeds from digital images: A support vector machine approach. Crop Protection, 40: 98-104.
2- Alchanatis V., Ridel L., Hetzroni A., and Yaroslavsky L. 2005. Weed detection in multi-spectral images of cotton fields. Computers and Electronics in Agriculture, 47: 243-260.
3- Andújar D., Weis M., and Gerhards R. 2012. An Ultrasonic System for Weed Detection in Cereal Crops. Sensors, 12: 17343-17357.
4- Andujar D., Escol ÀA., Dorado J., and Fernandez-Quintanilla C. 2011. Weed discrimination using ultrasonic sensors. Weed Research, 51: 543-547.
5- Burgos-Artizzu X. P., Ribeiro A., Guijarro M., and Pajares G. 2011. Real-time image processing for crop/weed discrimination in maize fields. Computers and Electronics in Agriculture, 75: 337-346.
6- Burgos-Artizzu X. P., Ribeiro A., Tellaeche A., Pajares G., and Fernandez-Quintanilla C. 2010. Analysis of natural images processing for the extraction of agricultural elements. Image and Vision Computing, 28: 138-149.
7- Escolà A., Andújar D., Dorado J., Fernandez-Quintanilla C., and Rosell-Polo J. R. Weed detection and discrimination in maize fields using ultrasonic and lidar sensors.
8- Fricke T., Richter F., and Wachendorf M. 2011. Assessment of forage mass from grassland swards by height measurement using an ultrasonic sensor. Computers and Electronics in Agriculture, 79: 142-152.
9- Gee C., Bossu J., Jones G., and Truchetet F. 2008. Crop/weed discrimination in perspective agronomic images. Computers and Electronics in Agriculture, 60: 49-59.
10- Harper N., and McKerrow P. 2001. Recognising plants with ultrasonic sensing for mobile robot navigation. Robotics and Autonomous Systems, 34: 71-82.
11- Harper N. L., and McKerrow P. J. 1997. Recognition of Plants with CTFM Ultrasonic Range Data using a Neural Network. International Conference on Robotics and Automation,
12- Henten E. J. v., Asselt C. J. v., Bakker T., Blaauw S. K., Govers M. H. A. M., J.W. Hofstee1, Jansen R. M. C., Nieuwenhuizen A. T., Speetjens S. L., Stigter J. D., Straten G. v., and Willigenburg L. G. V. WURKing: a small sized autonomous robot for the Farm of the Future.
13- Jones G., Gee C., and Truchetet F. 2009. Assessment of an inter-row weed infestation rate on simulated agronomic images. Computers and Electronics in Agriculture, 67: 43-50.
14- Kay L. 1974. A sonar aid to enhance spatial perception of the blind: engineering design and evaluation. Radio and Electronic Engineer, 44: 605-627.
15- Maeyama S., Ohya A., and Yuta S. i. 1994. Positioning by Tree Detection Sensor and Dead Reckoning for Outdoor Navigation of a Mobile Robot. International Conference on Multisensor Fusion and Integration for Intelligent Systems,
16- McKerrow P., and Yoong K. K. 2007. Classifying still faces with ultrasonic sensing. Robotics and Autonomous Systems, 55: 702-710.
17- Mizrach A. 2008. Ultrasonic technology for quality evaluation of fresh fruit and vegetables in pre- and postharvest processes. Postharvest Biology and Technology, 48: 315-330.
18- Montalvo M., Guerrero J. M., Romeo J., Emmi L., Guijarro M., and Pajares G. 2013. Automatic expert system for weeds/crops identification in images from maize fields. Expert Systems with Applications, 40: 75-82.
19- Perez A. J., Lopez F., Benlloch J. V., and Christensen S. 2000. Colour and shape analysis techniques for weed detection in cereal fields. Computers and Electronics in Agriculture, 25: 197-212.
20- Wu X., Xu W., Song Y., and Cai M. 2011. A Detection Method of Weed in Wheat Field on Machine Vision. Procedia Engineering, 15: 1998-2003.
21- Zamahn Q. U., and Salyani M. 2004. Effects of foliage density and ground speed on ultrasonic measurement of citrus tree volume. American Society of Agricultural Engineers,
22- Zarifneshat S., Rohani A., Ghassemzadeh H. R., Sadeghi M., Ahmadi E., and Zarifneshat M. 2012. Predictions of apple bruise volume using artificial neural network. Computers and Electronics in Agriculture, 82: 75-86.