Poetry groups and movements or schools may be self-identified by the poets that form them or defined by critics who see unifying characteristics of a body of work by more than one poet. To be a 'school' a group of poets must share a common style or a common ethos. A commonality of form is not in itself sufficient to define a school; for example, Edward Lear, George du Maurier and Ogden Nash do not form a school simply because they all wrote limericks.