@MISC{GROUP_11.MIZ,
  AUTHOR = {Liang, Xiquan and Li, Dailu},
  TITLE = {On Rough Subgroup of a Group},
  DAY = {7},
  MONTH = {August},
  YEAR = {2009},
  ADDRESS1 = {Department of Mathematics and Physics\\
           Qingdao University of Science and Technology\\China},
  ADDRESS2 = {Department of Mathematics and Physics\\
           Qingdao University of Science and Technology\\China},
  SUMMARY = {This article describes a rough subgroup with respect
            to a normal subgroup of a group, and some properties
            of the lower and the upper approximations in a group.}}

