Even using the simple watermarking method described, it can be difficult to distinguish some watermarks. They include intaglio printing, holograms, microprinting, fluorescent ink, latent images, watermarks, and angle-sensitive ink. Security features include holographic images, micro printing, UV-visible features, watermarks, etc. Digital watermarks are steganographically embedded within audio or video data during production or distribution. Other security features include watermarks, perforated passport numbering, embedded security fibers, among others. Electronic watermarks, embedded in a file, protect use rights for Internet content. Tall leaded windows feature 35 foot stained glass panels reproducing Renaissance watermarks. Some university and college transcripts have special anti-copying watermarks in the background. Detecting watermarks in a video can indicate the source of an unauthorized copy. Philatelically, there are several descriptive terms used to categorize watermarks. The word is also used for digital practices that share similarities with physical watermarks. The paper was originally handmade and displayed the characteristic watermarks. He developed a method of detecting forged watermarks in 1915. Next, comparing watermarks with those contained in catalogs or trade listings can yield useful results. Other researchers believe they became suspicious of paper with anachronistic watermarks.