  We consider anisotropic self-similar random fields, in particular, the
fractional Brownian sheet. This Gaussian field is an extension of fractional
Brownian motion. We prove some properties of covariance function for
self-similar fields with rectangular increments. Using Lamperti transformation
we obtain properties of covariance function for the corresponding stationary
fields. We present an example of a Gaussian self-similar field with stationary
rectangular increments that is not a fractional Brownian sheet.
