Variation

Selection: The Mechanism of Evolution

Graham Bell

The Development of Standard English, 1300-1800: Theories, Descriptions, Conflicts (Studies in English Language)

Laura Wright

The Handbook of World Englishes

Language Universals and Variation

Mengistu Amberber,Peter Collins (Editors)

Language Change, Variation, and Universals

Peter W. Culicover

The Light Curve of XX Cygni As a Contribution to the Study of Cepheid Variation (1915)(en)(5s)

Shapley S.

Heredity

Clarke, C A