This illustration depicts an object graph of "person_t" instances. There are six objects. The first object ("person1") refers to two other objects (M "person2" and F "person3"). The second object (M "person2") also refers to two other objects (M "person4" and F "person5"). The third object (F "person3") refers to only one object (F "person6") as its other reference to (M) is a NULL reference.