I went to a library... and asked the librarian if they had a book on Pavlov's dogs and Schrodinger's cat. She said, ""Well it rings a bell but I'm not sure if it's there or not.""

I asked a librarian for a book about Pavlov's dogs and Schrodinger's cat... She said it rang a bell but she didn't know if it was there or not.

One year later after Pavlov's dog death... Pavlov still brings him food.

A man goes into a library and asks for a book about Pavlov's dogs and Schrodinger's cat. The librarian says, ""It rings a bell, but I don't know whether it's there or not.""