?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aulast=Tang&rft.aufirst=J&rft.au=Tang%2C+J&rft.title=IEEE+Transactions+on+Vehicular+Technology&rft.issn=0018-9545&rft.pages=2439-2453&rft.issue=3&rft.date=March+2018&rft.atitle=Energy-Efficient+Heterogeneous+Cellular+Networks+with+Spectrum+Underlay+and+Overlay+Access&rft.volume=67&rft.genre=article