I just answered this question with links and quotes. The real in-detail explanation, seen in the second link in my answer, would be very big. Does it make sense to copy & paste such a huge explanation or is the link enough? Normally I dont like it to just put in links without a quote because they could be offline any time soon.
A link is never just enough, for the reason you stated. Other pages can move, change or be deleted without warning, potentially rendering an answer useless.
Quoting the information is fine and stops this from happening. Reading the information and summarising it so it specifically answers the question is even better but not mandatory if the quote is clear and answers the question.