"a relationship which" is correct and usable in written English.
It is used to refer to a specific relationship previously mentioned. For example, "She was in a relationship which had ended badly."
That ended up to be a relationship which was extremely simpatico.
Their tanglings and separations suggested a relationship, which made the dance more vivid.
What was the point in covering up a relationship which was already in the public domain?
Somehow a relationship which began as servitude turned into one of loyalty and mutual esteem.
"You cannot have a relationship which is tilted toward one country," he said.
Most curiously, it's a relationship which has brought both men a seemingly endless supply of cool.
Resonator dimensions play an important role in NAM-IR, a relationship which will be elaborated here.
And I thought, this is a relationship which is crumbling and she's not too aware of it.
And the financial benefits from such a relationship, which come from referrals, build up significantly over the years.
But hostility goes back much further in a relationship which Iranians sometimes admit has an obsessive quality.
When it hatches, he finds an affinity with the beast, a relationship which develops through the book.
