The Chronicles of Thomas Covenant is a series of ten high fantasy novels written by American author Stephen R. Donaldson. The series began as a trilogy, entitled "The Chronicles of Thomas Covenant, the Unbeliever". This was followed by another trilogy, "The Second Chronicles of Thomas Covenant", and finally a tetralogy, "The Last Chronicles of Thomas Covenant".
Stephen R. Donaldson has written three separate novel trilogies 
The context tells us he has written two, but doesn't tell us about any other series he has written. It is only using the context given instead of the context not given