Handbook of Liturgical Practice of the Russian Church Abroad
When a Priest and Deacon concelebrate, the Deacon reads the entrance prayers with the Priest giving the blessings and exclamations in the usual way. The Priest stands immediately before the Royal Doors, the Deacon to his right and slightly behind him.
When multiple Priests and Deacons concelebrate, the senior Deacon alone reads the prayers, and the senior Priest alone the blessings and exclamations; the others remain silent. The senior Priest stands immediately before the Royal Doors, the Deacon immediately to his right and slightly behind him, and the other Priests to their right and left.
When multiple Priests concelebrate without a Deacon, the senior Priest alone reads all the entrance prayers and exclamations. He stands before the Royal Doors with the other Priests to his right and left.