1. Effects of vitamin A acid on transplantable and chemically induced tumors;Bollag;Cancer Chemother. Rep.,1971
2. Vitamin A-Säure in der Tumortherapie;Bollag;Schweiz. med. Wschr.,1971
3. Prophylaxis of chemically induced benign and malignant epithelial tumors by vitamin A acid (retinoic acid);Bollag;Europ. J. Cancer,1972
4. Therapy of actinic keratoses and basal cell carcinomas with local applications of vitamin A acid;Bollag;Cancer Chemother. Rep.,1971
5. Die perorale Anwendung von Vitamin A-Säure bei Leukoplakien, Hyperkeratosen und Plattenepithelkarzinomen: Ergebnisse und Verträglichkeit;Ryssel;Schweiz. med. Wschr.,1971