My book (Andrew S. Tanenbaum, “Computer Networks”, Fifth Edition.) takes that as the definition of "Computer Networks".
I was able to find out that by autonomous computers, it's referring to those that have no control over one another but I don't see why this is a restriction.
For "single technology", I'm not sure what this exactly is talking about. I don't know what is an example of a network that incorporates "multiple technologies" and again I don't know why this is a restriciton.