Adaptive Output Feedback based on Closed-loop Reference Models
  This note presents the design and analysis of an adaptive controller for a class of linear plants in the presence of output feedback. This controller makes use of a closed-loop reference model as an observer, and guarantees global stability and asymptotic output tracking. 
Travis E. Gibson and Zheng Qu and Anuradha M. Annaswamy and Eugene   Lavretsky
cs.SY math.OC nlin.AO