Librarian Note: There is more than one author in the GoodReads database with this name. A pseudonym used by Mildred Benson, aka Mildred A. Wirt. The stand-alone book Connie Carl at Rainbow Ranch and the Penny Nichols series was originally published from 1936 to 1939 by the Goldsmith Publishing Company. The series was written by Mildred Wirt Benson under the pseudonym of Joan Clark. The series consists of four titles: 1. Penny Nichols Finds a Clue, 1936 2. Penny Nichols and the Mystery of the Lost Key, 1936 3. Penny Nichols and the Black Imp, 1936 4. Penny Nichols and the Knob Hill Mystery, 1939