Temporal evolutions of orbital elements for two comets that made significant visits into retrograde orbits, using the number of orbits as time variable. The time frames cover several thousand orbits before the comets become retrograde and significantly less afterwards. Two panels are shown for each comet: the upper panel exhibits the semi-major axis a (au), the eccentricity e, the inclination i and the argument of perihelion ω, while the lower panel shows the quantity L_z = (1−e²)^1/2cosi, expressing the vertical component of the angular momentum, and the critical arguments of the ν₁₆ and ν₅ secular resonances. The colour codings are shown to the right. Angles are labelled on the left and the other quantities on the right.