https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjppLbCob7MAhXRB44KHVKnBzsQFggcMAA&url=http%3A%2F%2Fwww.photonics.ucla.edu%2Fmedia%2Fpublication%2Fjournal%2F101109JLT2005850787.pdf&usg=AFQjCNEdTuz2Hv3aUvddrY4lL7Z9YtP8gQ&sig2=D_IQLBDC0R3eo10I4wzo1Q
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjppLbCob7MAhXRB44KHVKnBzsQFgglMAE&url=https%3A%2F%2Farxiv.org%2Fpdf%2F1304.0422&usg=AFQjCNEijKNreDWkNSba5HnJnanHOhz7rA&sig2=4Jizsjpjm4P-D1BytGe0TA
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjppLbCob7MAhXRB44KHVKnBzsQFggsMAI&url=http%3A%2F%2Fwww.bu.edu%2Fsmartlighting%2Fresearch%2Foptical-mimo%2F&usg=AFQjCNH_veGwu0J_Gxe7UJ-riERv35q51g&sig2=lBc3a29wL204DCIy7i2a_Q