Stacking of the titles as seen in countries such as Germany (Prof. Dr. Dr. Dr. Gruber) is highly uncommon in the Netherlands and not well received culturally. Those who have multiple doctor titles may use dr.mult. before their name, but this is seldomly seen in practice. The honoris cause doctors may use dr.h.c. before their name. Combining different Dutch titles, especially in different disciplines, is allowed however (e.g. mr. dr. Jansen, dr. mr. Jansen, dr. ir. Jansen, mr. ir. drs. Jansen, mr. ir. Jansen). The use of the combination ir. ing. is frequent, indicating one holds a HBO, vocational (or professional) engineering degree together with an academic engineering degree. What is not allowed is, after obtaining a doctorate, using dr. drs. Jansen; dr. Jansen should be used instead.