Rainero I, Rivoiro C, Gallone S, Valfrè W, Ferrero M, Angilella G, Rubino E, De Martino P, Savi L, Lo Giudice R, Pinessi L. Lack of association between the 3092 T-->C Clock gene polymorphism and cluster headache. Cephalalgia. 2005 Nov;25(11):1078–81. doi: 10.1111/j.1468-2982.2005.00965.x. PMID: 16232160.