title: Permanence of populations in a polluted environment.
abstract: Studies of several population-toxicant models are discussed. Under the hypothesis that the exogenous input of toxicant into the environment is periodic in time, the conditions for permanence of populations are obtained.
authors.affiliation: Department of Mathematics, Southwest Normal University, Chongquing, People's Republic of China.
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Ma
mesh_terms: D000818:Animals; D004787:Environmental Pollution; D008962:Models, Theoretical; D011157:Population Dynamics; D013997:Time Factors