[1] CONRAD P.: 
The structure of a lattice ordered group with a finite number of disjoint elements. Michigan Math. J. 7, 1960, 171-180. 
MR 0116059 | 
Zbl 0103.01501[2] CONRAD P.: 
Some structure theorems for lattice ordered groups. Trans. Amer. Math. Soc. 99, 1961, 212-240. 
MR 0121405 | 
Zbl 0099.25401[3] CONRAD P.: 
Lattice ordered groups. Tulane University 1968. 
Zbl 0155.05902[4] FUCHS L.: 
Partially ordered alebraic systems. Oxford 1963. 
MR 0171864