Complex sentence: Connie Blair is the central character in a series of 12 mystery novels for adolescent girls written by Betty Cavanna under the pseudonym Betsy Allen and published by Grosset & Dunlap between 1948 and 1958.
Split into simpler sentences: Connie Blair is the central character in a series of 12 mystery novels for adolescent girls written by Betty Cavanna under the pseudonym Betsy Allen. The series was published by Grosset & Dunlap between 1948 and 1958.