| Subject | English | German |
| opt. | Köhler method of illumination | Köhlersches Prinzip (method of microscopical illumination) |
| opt. | Köhler method of illumination | Köhlersches Beleuchtungsprinzip (method of microscopical illumination) |
| opt. | Köhler's method of illumination | Köhlersches Prinzip (method of microscopical illumination) |
| opt. | Köhler's method of illumination | Köhlersches Beleuchtungsprinzip (method of microscopical illumination) |