+\bibcite{ref17}{1}
+\bibcite{ref19}{2}
+\bibcite{berman04}{3}
+\bibcite{cardei2005improving}{4}
+\bibcite{cardei2005energy}{5}
+\bibcite{castano2013column}{6}
+\bibcite{conti2014mobile}{7}
+\bibcite{Deng2012}{8}
+\bibcite{deschinkel2012column}{9}
+\bibcite{idrees2014coverage}{10}
+\bibcite{jaggi2006}{11}
+\bibcite{kim2013maximum}{12}
+\bibcite{Kumar:2005}{13}
+\bibcite{li2013survey}{14}
+\bibcite{ling2009energy}{15}
+\bibcite{pujari2011high}{16}
+\bibcite{Misra}{17}
+\bibcite{Nayak04}{18}
+\bibcite{pc10}{19}
+\bibcite{pedraza2006}{20}
+\bibcite{qu2013distributed}{21}
+\bibcite{raghunathan2002energy}{22}
+\bibcite{ref22}{23}
+\bibcite{rossi2012exact}{24}
+\bibcite{varga}{25}
+\bibcite{chin2007}{26}
+\bibcite{ChinhVu}{27}
+\bibcite{5714480}{28}
+\bibcite{xu2001geography}{29}
+\bibcite{yang2014novel}{30}
+\bibcite{yangnovel}{31}
+\bibcite{Yang2014}{32}
+\bibcite{Zhang05}{33}
+\bibcite{zorbas2010solving}{34}