The following reference works are cited in this example problem:
- Craig, R.R. & Bampton, M. D. D. (1968). Coupling of substructures for
                    dynamic analysis. AIAA Journal. 6(7),
                    1313-1319. 
- Craig, R.R. (1987). A review of time domain and frequency domain component
                    mode synthesis methods. International Journal of
                        Analytical and Experimental Modal Analysis. 2(2), 59-67.