Before revision:  We propose a simple two-step estimation strategy, establish the asymptotic properties of the proposed estimators , and prove the validity of a computationally convenient bootstrap procedure to conduct asymptotically valid simultaneous (instead of pointwise) inference.
After revision:  We propose a simple two-step estimation strategy, establish the asymptotic properties of the proposed estimators and prove the validity of a computationally convenient bootstrap procedure to conduct asymptotically valid simultaneous (instead of pointwise) inference.