The theory of infinite soluble groups by Lennox, John C. (John Carson), Robinson, Derek John Scott

Available for University of the Philippines System via Oxford Scholarship Online. Click here to access.

The theory of infinite soluble groups by Lennox, John C., Robinson, Derek J. S.

Available for University of the Philippines Diliman via Oxford Scholarship Online. Click here to access:

Finite soluble groups. by Doerk, Klaus

On products of normal supersoluble subgroups and generalisations by Perez, Edmundo R.

On equioptimal groups by Petalcorin, Gaudencio C. 1965-