Summary: We study three self-similar, long-range dependent Gaussian processes. The first one, with covariance
parameters , , , corresponds to fractional Brownian motion for , . The second one, with covariance
parameter , corresponds to sub-fractional Brownian motion for . The third one, with covariance
is related to the second one. These processes come from occupation time fluctuations of certain particle systems for some values of the parameters.