an international journal Volume 103 Number1 February 1991 J. H. Swart anv H. C. Murrext (Durban, South Africa) A Mode! of Age-Dependent Population Dynamics Providing Simple Criteria for Growth or Extinction Davip ABRAHAM KAULT AND LACHLAN McLeop MarsH (Townsville, Australia) Modeling AIDS as a Function of Other Sexually Transmitted Disease RIcHARD E. Neapouitan (Chicago, IL) The Principle of Interval Constraints: A Generalization of the Symmetric Dirichlet Distribution Rosert E. ULanowicz (Solomons, MD) anp Wi-rriep F. WoLFF (Jilich, Germany) omepetees Poem Peesats Lawted Tae onc oc cccccecsecccsvesncwcnsees 45 James A. CAVENDER (Denver, CO) Necessary Conditions for the Method of Inferring Phylogeny by Linear Invariants Li-Qun ZHANG, JERRY C. CoLLins, AND Paut H. Kinc (Nashville, TN) Indistinguishability and Identifiability Analysis of Linear Compartmental Models Cauixto P. CALDEROGN AND Tor A. KwemMBE (Chicago IL) Modeling Tumor Growth L. E. HARNEVo AND Z. AGurR (Rehovot, Israel) The Dynamics of Gene Amplification Described as a Multitype Compartmental Model and as a Branching Process Cun Lone Cuianc (Berkeley, CA) A True Rate of Population Growth—Lotka’s Intrinsic Rate of Natural Increase Revisited Book Review BarpD ERMENTROUT (Pittsburgh, PA) Mathematical Biology (J, D. Murray) ANNOUNCEMENTS