Qualcomm Incorporated, LTE advanced: heterogeneous networks, Feb. 2010. Availalbe: http://www.qualcomm.co.kr/documents/lteadvanced-heterogeneous-networks.
 Y. Wang, K. I. Pedersen, T. B. Sorensen and P. E. Mogensen, “Carrier Load Balancing and Packet Scheduling for Multi-carrier Systems,” IEEE Transactions Wireless Communications, Vol. 9, 2010, pp. 1780-1789. doi:10.1109/TWC.2010.05.091310
 K. I. Pedersen, F. Frederiksen, C. Rosa and H. Nguyen, Carrier Aggregation for LTE-advanced: Functionality and Performance Aspects, IEEE Communications Magazine, Vol. 49, No. 6, 2011, pp. 89-95. doi:10.1109/MCOM.2011.5783991
 A. Barbieri, P. Gaal, S. Geirhofer, T. Ji, D. Malladi, Y. Wei and F. Xue, “Coordinated Downlink Multi-point Communications in Heterogeneous Cellular Networks,” Information Theory and Applications Workshop (ITA), 2012, pp. 7-16.
 W. Seo, S. Choi and D. Hong, “A Beam-forming Codebook Restriction for Cross-Tier Interference Coordination in Two-Tier Femtocell Networks,” IEEE Transactions on Vehicular Technology, Vol. 60, No. 4, pp. 1651-166.