On optimality and construction of circular repeated-measurements designs
  The aim of this paper is to characterize and construct universally optimal designs among the class of circular repeated-measurements designs when the parameters do not permit balance for carry-over effects. It is shown that some circular weakly neighbour balanced designs defined by Filipiak and Markiewicz These results extend the work of Magda, Kunert, Filipiak and Markiewicz. 
R. A. Bailey, Peter J. Cameron, Katarzyna Filipiak, Joachim Kunert,   Augustyn Markiewicz
math.ST math.CO stat.TH