The connection among sets recognized by ? known as inclusion or containment. Equality between sets can be expressed with regards to subsets.B?n có th? ch?n th?c ??n s?n có ho?c ??a ra yêu c?u riêng, c?a ti?m s? t? v?n k? l??ng và ?i?u ch?nh linh ho?t ?? ?áp ?ng tr?n v?n mong mu?n c?a gia ch?.Nên tham kh?o các m?u v?n kh?n truy?n th?ng ho?c