Determining whether certain affine Deligne-Lusztig sets are empty

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Let F be a non-archimedean local field, let L be the maximal unramified extension of F, and let fr be the Frobenius automorphism. Let G be a split connected reductive group over F, and let B(1) be the Bruhat-Tits building associated to G(F). We know that fr acts on G(L) with fixed points G(F). Let I be the Iwahori associated to a chamber in B(1). We have the relative position map, inv, from G(L)/I x G(L)/I to the extended affine Weyl group, Wₑ of G. If w is in Wₑ and b is in G(L), then the affine Deligne-Lusztig set Xw(b fr) is x in G(L)/I: inv(x,b fr(x)) = w. This paper answers the question of which Xw(b fr) are non-empty for certain G and b.