Werke:
- Collected writings, Vol. 3.. German and Austrian art of the 15th and 16th centuries
- The art of the Renaissance in Northern Europe : its relation to the contemporary spiritual and intellectual movements
- Rembrandt : [Biographisch-krit. Studie]
- Collected writings, Vol. 4.. German and Austrian baroque art, art of the 19th and 20th centuries, museums and collections, monument service, theoretical writings on the history of art, museology and...