Aaron, F. D., Alexa, C., Andreev, V., Backovic, S., Baghdasaryan, A., Baghdasaryana, S., et al. (2011). Search for first generation leptoquarks in ep collisions at HERA. Physics Letters B, 704(5), 388-396. doi:10.1016/j.physletb.2011.09.017.