Interesting articles that are worth reading:

• In my opinion a very good article on the castration of male dogs (in German): „Die Kastration des Rüden aus verhaltensbiologischer Sicht“; Tierärztin Sophie Strodtbeck und Verhaltensbiologe Dr. Udo Gansloßer; wuff.at

Books related to canine topics in general and dog training that I can recommend:

• Susanne Reinerth: „Natural Dog Food“ (Nutrition)
• Turid Rugaas: „Calming Signals“ (Training)
• Anke Bogaerts: „Die drei Charaktere“ (Training)