The lexicographic product of po-groups and $n$-perfect pseudo effect   algebras
  We will study the existence of different types of the Riesz Decomposition Property for the lexicographic product of two partially ordered groups. A special attention will be paid to the lexicographic product of the group of the integers with an arbitrary po-group. Then we apply these results to the study of $n$-perfect pseudo effect algebras. We show that the category of strong $n$-perfect pseudo-effect algebras is categorically equivalent to the category of torsion-free directed partially ordered groups with RDP$_1.$ 
A. Dvure\v{c}enskij, J. Kr\v{n}\'avek
math-ph math.MP