I'm looking to perform a set operation in a Neo4j cypher. Basically I have relationships to a set of nodes from two directions, I want to find only nodes on one side which have a relationship to all those on the other.

Given a graph similar to the following:

```
  /----- b1 -\
 /            \
a ------ b2 --c1
 \          \/
  \         /\
   \---- b3 --c2     

```

I would only like `c1` to be returned, as `c2` does have a direct relationship with `b1` while `a` does.