Wisconsin Potato Salad
["2 1/2 lb. potatoes", "1/3 c. cider vinegar", "1/4 c. corn oil", "2 Tbsp. sugar", "1 tsp. salt", "1/4 tsp. pepper", "4 hard-cooked eggs, chopped", "1/3 c. finely chopped onion", "2 Tbsp. minced parsley", "1/2 c. mayonnaise"]
["Cook washed, unpared potatoes in salted water until tender. Meanwhile, in a small mixing bowl with a fork, beat together the vinegar, corn oil, sugar, salt and pepper; set aside but beat together again just before using."]
["potatoes", "cider vinegar", "corn oil", "sugar", "salt", "pepper", "eggs", "onion", "parsley", "mayonnaise"]