"Prediction is very difficult, especially about the future." -- Niels Bohr
This is mistakenly attributed to Bohr by numerous sources, including yours, and articles in newspapers and academic journals, due to popularity as a Danish proverb. It's not original to Bohr.
Btw, my wife is Danish, and is familiar with the proverb, so she laughed at me when I offered the quote as from Niels Bohr.
It's a Danish proverb, and since Neils Bohr was Danish, and since fellow physicists claim he said it, it's reasonable to assume he actually said it and therefore, it is a valid quote.
"my wife is Danish" - fauxlaw
That is a valid quote because you actually said it, even though I suspect you aren't the first person to have ever said it.