 The first is leveraging contraction theory and a new type of contraction metric that , when coupled with an adaptation law, is able to track feasible trajectories generated by an adapting reference model.
<clarity>  The first is leveraging contraction theory and a new type of contraction metric that , when coupled with an adaptation law, is able to track feasible trajectories generated by an adapting reference model.
 The first is introducing parameter-dependent storage functions that guarantee closed-loop tracking of a desired trajectory generated by an adapting reference model.