Torsion points on elliptic curves defined over quadratic fields

Let k be a quadratic field and E an elliptic curve defined over k . The authors [8, 12, 13] [23] discussed the k -rational points on E of prime power order. For a prime number p , let n = n(k, p ) be the least non negative integer such that for all elliptic curves E defined over a quadratic field k ([15]).