The reference paper used is [1], with the corrections suggested by [2]
[1] J. E. Hopcroft, R. E. Tarjan: Dividing a Graph into Triconnected Components. SIAM J. Comput. 2(3): 135-158
[2] C. Gutwenger, P. Mutzel: A Linear Time Implementation of SPQR-Trees. Graph Drawing 2000: 77-90