Superimposition of two surfaces of section obtained by ${\overline{H}}_{\text{Fourier}}$ and ${\overline{H}}_{\text{Schubart}}$, respectively. The red dots mark the intersection points with the section θ₁ = 0 of the flows of the system ${\overline{H}}_{\text{Fourier}}$ using the initial conditions in the set S₁. The black dots mark the intersection points with the section ${\overline{Q}}_1=0$ of the flows of the system ${\overline{H}}_{\text{Schubart}}$ using the initial conditions in the set S₂.