Submission of the Emperor Frederick Barbarossa to Pope Alexander III by Federico Zuccaro https://www.rawpixel.com/image/8978619/image-paper-person-artFree Image from public domain licenseThe Emperor Frederick Barbarossa Submitting to Pope Alexander III in the Presence of a Doge https://www.rawpixel.com/image/9328453/image-paper-art-vintageFree Image from public domain licenseThe Submission of the Emperor Frederick Barbarossa to Pope Alexander III by Federico Zuccaro https://www.rawpixel.com/image/14246945/image-dogs-face-personFree Image from public domain license