New Results on Fourth-Order Differential Subordination and Superordination for Univalent Analytic Functions Involving a Linear Operator.

We present several new results for fourth-order differential subordination and superordination in this paper by using the differential linear operator Γ π , ρ , β , μ f z . Relevant connections between the new results presented here and those considered in previous works are addressed. The properties and results concerning the differential subordination theory are symmetric to the properties obtained using the differential superordination theory, and by combining them, sandwich-type theorems are obtained. [ABSTRACT FROM AUTHOR]