Two-parameter bifurcations diagram in plane ðf,mÞ with PO and PR. Black colour indicates one attractor (for locked PO, excluding 4 : 3 resonance,
between period doubling bifurcation lines on the left and right sides—edges of the resonance tongues), grey colour shows two coexisting attractors (the
same as for black but with coexisting stable steady state of the pendulum). In the hatched area we observe the coexistence of stable rotations (three areas
with: pairs of symmetric 1 : 1 or 1 : 3 or 1L1R PR) and stable steady state of the pendulum