Complex Sentence Stuff is a resource book written by Australian speech pathologists that includes conjunctions (or, while, unless, although) and relative clauses (who, that, which). It is a resource book designed to help children learn to use conjunctions in their written and oral language.
There are five chapters in the book including 4 different conjunction chapters and worksheets for all four in a mixed chapter. This book also has a supplementary chapter on relative clauses. This targets children's use of "who", "that" and "which". The book is over 100 pages.