was an obvious REFERENCE
The Big Bang Theory Season 7, Episode 3
...you'd be in a non-inertial
REFERENCE frame and would...
The Big Bang Theory Season 1, Episode 3
...you might wanna skip the REFERENCE
to bowel movements.
The Big Bang Theory Season 1, Episode 1
That is a cleverly veiled REFERENCE
to Howard's lifelong obsession...
The Big Bang Theory Season 6, Episode 9
Is that a REFERENCE
to my speech impediment?
The Big Bang Theory Season 7, Episode 10