Walker, E., & Elsworth, S. (1998). Grammar practice for elementary students.
Citazione stile Chigago Style (17a edizione)Walker, Elaine, e Steve Elsworth. Grammar Practice for Elementary Students. Harlow, 1998.
Citatione MLA (9a ed.)Walker, Elaine, e Steve Elsworth. Grammar Practice for Elementary Students. 1998.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.