Brian Alspach Heather Gavlas Mateja Sajna Helen Verrall Cycle decompositions IV: complete directed graphs and fixed length directed cycles. 165-208 2003 103 J. Comb. Theory, Ser. A 1 http://dx.doi.org/10.1016/S0097-3165(03)00098-0 db/journals/jct/jcta103.html#AlspachGSV03