I had only known "whose clauses".
I love the car whose lines are beautiful.
When I came to this kind of sentence, I always be awkward since the clause subject is inanimate.
I just know the second way "of which". This expression is good. Unexpectedly, there is the 3rd way - "which's" - given by the same website.
The car which's lines are sleek is beautiful.
I had thought "which's" is a wrong way, never thought there is such a way. And I rarely see much of this usage. Did you see it in somewhere?