Complex sentence: He kept up his writing for "The New Age", with "War Notes" written under the pen name "North Staffs", and "A Notebook", which contains some of his most organised critical writing.
Split into simpler sentences: He kept up his writing for "The New Age". Notable publications during this period were for that magazine were "War Notes," written under the pen name "North Staffs", and "A Notebook", which contains some of his most organised critical writing.