public boolean check_Authors(){
        	boolean nameValid = false;
        	int counter = 0;
        	for (int i =0; i<authors.size(); i++){
        		if (!authors.get(i).getName().isEmpty() && authors.get(i).getName() != null){
        			counter ++;
        		}
        	}
        	if (authors.size()==0){
        		nameValid = false;
        	}
        	else if (counter==authors.size()){
        		nameValid = true;
        	}
        	else {
        		nameValid = false;
        	}
        	
        	return nameValid;
        }