Sources:
To enhance the learning experience, we have sometimes used videos from third-parties, such as YouTube and Vimeo. If you believe we are using your material without consulting or agreement, please let us know by sending an email to rail@tudelft.nl. After we receive your request and proof of ownership, we will replace the material within 72 hours. We apologise for the inconvenience and thank you for your understanding in this matter.
Imagery used throughout the course is a combination of our own material, images from our partners and, in some cases, creative commons images provided by external sources.
For those people (and companies) who allowing us to use their material explicitly or via the creative commons license agreement, we are extremely grateful. Railway Engineering wouldn't be possible without the wheel, and we are glad that we didn't need to reinvent it (or the many excellent references to it that you have provided).