What is the correct order of ionic radii of Y3+, La3+,Eu3+ and Lu3+ ?

The correct order of ionic radii of Y³⁺,La³⁺,Eu³⁺ and Lu³⁺, is Y³⁺ < Lu³⁺ < Eu³⁺ < La³⁺ because Eu and Lu are the members of lanthanide series (so they show lanthanide contraction) and La is the representative element of all elements of such series and Y³⁺ ion has lower radii as comparison to La³⁺ because it lies immediately above it in the periodic table.