Perhaps you should try some spelling variations:
"probabilistic rough sets over _ universes" » "probabilistic risk sets over _ universes", "probabilistic approach sets over _ universes", "probabilistic roadmap sets over _ universes"
"probabilistic rough set over _ universes" » "probabilistic risk set over _ universes", "probabilistic approach set over _ universes", "probabilistic roadmap set over _ universes", "probabilistic rough set cover _ universes"

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