Progress feedback in children and adolescents with internalizing and externalizing symptoms in routine care (OPTIE study): study protocol of a randomized parallel-group trial oleh Christopher Hautmann, Jana Rausch, Nina Geldermann, Felix Oswald, Danny Gehlen, Martin Hellmich, Kerstin Daniela Rosenberger, Christina Samel, Katrin Woitecki, Daniel Walter, Julia Adam, Lydia Dachs, Hildegard Goletz, Joya Halder, Claudia Kinnen, Kristina Mücke, Janina Otte, Daniela Perri, Christiane Rademacher, Stephanie Schürmann, Paula Viefhaus, Tanja Wolff Metternich-Kaizman, Manfred Döpfner