public void addRestrictionToEvent(String eventIdentifier, String restrictionIdentifier)
        {
        	//Get that restriction
        	Restriction restrictionToAdd = null;
        	for(Restriction r: restrictions){
        		if(r.getIdentifier().equals(restrictionIdentifier))
        			restrictionToAdd = r;
        		}
        	//Check that it exists
        	if(restrictionToAdd == null)
        		throw new IllegalArgumentException("There's no restriction with the identifier '"+restrictionIdentifier+"'.");
        	
        	for(Event e: events){
        		if(e.getIdentifier().equals(eventIdentifier))
        		{
        			//We check if the restriction is already there
        			for(Restriction r: e.getRestrictions()){
                		if(r.getIdentifier().equals(restrictionIdentifier))
                			throw new IllegalArgumentException("There's already a restriction with that identifier. Identifiers need to be unique.");
                		}
        			//If not, just add it
        			e.getRestrictions().add(restrictionToAdd);
        			return;
        		}	
        	}
        	throw new IllegalArgumentException("There's no event with the identifier '"+eventIdentifier+"'.");
        }