@Override
	public boolean equals(Object obj) {
		boolean equal = false;
		
		if(obj != null && obj instanceof SubjectID) {
			SubjectID right = (SubjectID) obj;
			
			if(right.contributor != null && right.value != null && this.contributor != null && this.value != null) {
				equal = this.contributor.equals(right.contributor) && this.value.equals(right.value);
			}
		}
		
		return equal;
	}