Ren Ping Liu Zvi Rosberg Iain B. Collings Carol Wilson Alex Y. Dong Sanjay Jha Energy Efficient Reliable Data Collection in Wireless Sensor Networks with Asymmetric Links. 131-141 2009 16 IJWIN 3 http://springerlink.metapress.com/content/237u821701303310/ db/journals/ijwin/ijwin16.html#LiuRCWDJ09