Comparison of the Hα line profiles computed by our code (grey line) with the observation of SDSS J094321.97+042412.0. The parameters are: i= 17°, n1= 2.1π, n2= 3.0, n3= 24°, γ0= 202°, the disc zone is from Rin= 250rg to Rout= 1000rg for a retrograde disc.