Locations and resonant configurations of the symmetric ACR family (S₆) and the asymmetric ACR family (A₆). In the upper two panels (a) and (b), the stable symmetric, unstable symmetric, and stable asymmetric ACRs are indicated by blue solid, red solid, and black dashed lines, respectively. Three solid circles on these lines indicate the initial conditions that will be analysed in detail later (see text). The lower two panels (c) and (d) show the evolutions of resonant angles along the asymmetric ACR as the function of δ (scaled AMD, see text). The resonant angles θ₁₂, θ₂₃ and the secular angles Δϖ₁₂, Δϖ₂₃ are labelled by the corresponding lines.