Before revision: They designed a set of problems to which the solution word was associated with all three words of the triad through formation of a compound word (or phrase) (e.g., age/mile/sand for the compounds stone age , milestone, and sandstone with the solution word stone).
After revision: They designed a set of problems to which the solution word was associated with all three words of the triad through formation of a compound word (or phrase) (e.g., age/mile/sand for the compounds Stone Age , milestone, and sandstone with the solution word stone).