Symbolic lumping of some catenary, mamillary and circular compartmental   systems
  Some of the most important compartmental systems, such as irreversible catenary, mamillary and circular systems are symbolically simplified by the method of exact linear lumping. A few symbolically unmanageable systems are numerically lumped. Transformation of the qualitative properties under lumping are also traced. 
E. Egri (1), J. T\'oth (2), C. Brochot (3), F. Y. Bois (3) ((1)   Babe\c{s}-Bolyai University, Department of Differential Eq...