TITLE: Eta Invariant of Spherical Space Form 
QUESTION [6 upvotes]: Is the eta invariant of spherical space form $\eta(S^3/\Gamma)$ always nonegative?
Can we calculate it with the information of $\Gamma\in SO(4)$ explicitly? 
In fact, i need a reference for the calculation of eta invariant. Can some one give me some advice or download the following paper for me? Thank you!
(1) Hitchin, N. J.(4-CAMB)
Einstein metrics and the eta-invariant. (Italian summary) 
Boll. Un. Mat. Ital. B (7) 11 (1997), no. 2, suppl., 95–105. 
(2) G.W. Gibbons, C.N. Pope
Index theorem boundary terms for gravitational instantons
Nuclear Physics B Volume 157, Issue 3, 1 October 1979, Pages 377–386.
Email: xuyiyan@math.pku.edu.cn

REPLY [3 votes]: The eta invariant of any locally symmetric space $\Gamma \backslash G/K$ is calculated by Moscovici and Stanton in Eta invariants of Dirac operators on locally symmetric manifolds. They related eta invariant with the conjugation class of $\Gamma$.