Independently but simultaneously evolved by Biot M A in US and H Ramberg in Uppsala in Sweden on buckling of a single layer enclosed in less viscous matrix. Although there were some basic differences in the two models, both arrived at the same final relationship that the buckling is dependent on the thickness of the layer and the viscosity contrast between layer and matrix. The Wd or dominant wavelength of a single layer is the arc length. The initial wavelength Wi may remain unchanged and become Wd in case the viscosity contrast is high. But Wi changes a good deal if the viscosity contrast is low and layer parallel strain operates.
Wd=2pt ( m 1/6m 2)^1/3