The authors formulate a 'partial realization' property and prove that this property is equivalent to the compact extension property. In addition, they prove that a linear space L has the compact extension property if and only if L is admissible if and only if L has the sigma-compact extension property. This implies that for a sigma-compact linear space L, the following statements are equivalent: (1) L is an absolute retract, (2) L has the compact extension property, and (3) L is admissible. Finally, it is proven that if there exists a linear space which is not an absolute retract, then there is an admissible linear space which is not an absolute retract.
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