From research undertaken in the 1950s by Murray with Professor Joe McNally, an educational psychologist at Manchester University, Murray realised that only 12 words account for ¼, 100 words account for ½, and 300 words account for ¾ of the words used in normal speaking, reading and writing in the English language.He developed 'The Key Words Reading Scheme,' a series of 36 English language early readers children's books, published by the British publishing company, Ladybird Books.