How can I find manuals for discontinued stereo equipment?

Looking at the motivation of the audio DIY participant, some think that it is cheaper to make equipment than it would cost if an item were bought new. Some do it for the enjoyment, spending much more time and money on a project than it would have cost to purchase something similar. Some think that they can just do a better job, or just want to create something unique or different. Reference: Veselinovic Article "DIY Pros and Cons".