"Mr. Musgrave" is a reference to "The Adventure of the Musgrave Ritual", one of Arthur Conan Doyle's Sherlock Holmes short stories.
When Sherlock speaks on the phone at his computer, he says the following in Norwegian: "Er kontorene deres åpne for publikum? Takk for det. Ha det bra". This translates to:"Are your offices open for the public? Thanks. Good Bye"
In Person of Interest, Ep. 2.20, Dennis Boutsikaris also played a man that reached out to authorities, claiming that he had been poisoned.