I am looking for work on systems that are similar to K. Dosen's higher-order sequents (Sequent Systems for Modal Logic, JSL 50).  The only work that I am aware of is recent work by Iemhoff and Metcalfe (Proof theory for admissible rules, Annals of Pure and Applied Logic 159 (1-2), 2009).Are there other papers on such systems?
Looking for papers and articles on higher-order sequent systems
reference request;lo.logic;proof theory