Study protocol of the multi-centre, randomised controlled trial of the Frankfurt Early Intervention Programme A-FFIP versus early intervention as usual for toddlers and preschool children with Autism Spectrum Disorder (A-FFIP study). - Kitzerow J; Hackbusch M; Jensen K; Kieser M; Noterdaeme M; Fröhlich U; Taurines R; Geißler J; Wolff N; Roessner V; Bast N; Teufel K; et al. (Trials, 2020)