Effects of a Pyralid pest on productivity of duckweeds in pond ecosystem / Shahnaz Imrana Belal [PhD Thesis] Belal, Shahnaz Imrana Duckweeds 584.64 BEE Thesis (Ph.D.) -- Department of Zoology, University of Dhaka, 2010-11 Includes bibliographical references Dhaka : University of Dhaka, 2014. 2014. 2014 Text xx, 202 p. : eng