GNSS RTK accuracy increasing consulting

I’m looking for a specialist in GNSS RTK
Consultation on methods for increasing the accuracy of the coordinates using three receivers GNSS RTK Receivers.
It is necessary to answer the question whether there are confirmed ways to raise the accuracy of the determination of coordinates by using three or more GNSS reveiver in static and kinematic mode.
Details: I have 3 GNSS receiver with closely located antena. Antennas are located in the corner of the triangle. Is it possible to determine the midpoint with high accuracy?
Your opinion should be confirmed by references to articles, pages and etc.
When applying, describe your experience in this field.