Amplitudes and recurrence times of normal dwarf nova outbursts and the Kukarkin-Parenago relation. Triangles: U Gem stars; square: PTF1 J0719+4858 (normal outburst); circles: V803 Cen and CR Boo (cycling state rebrightenings). Data from Warner (2003) and Ritter & Kolb (2003). The dotted lines represent the upper and lower uncertainty of the observational KP relation fitted to the systems marked on the plot while the two solid lines represent the theoretical KP relation for helium discs – the lower line has been calculated for α_h = 0.2, R_D = 0.7 × 10¹⁰ cm, M₁ = 1.0 and the upper line for α_h = 0.2, R_D = 1.0 × 10¹⁰ cm, M₁ = 1.2.