Hilbert's Tenth Problem (HTP) asked for an algorithm to test whether an arbitrary polynomial Diophantine equation with integer coefficients has solutions over the ring DOUBLE-STRUCK CAPITAL Z of integers. This was finally solved by Matiyasevich negatively in 1970. In this paper we obtain some further results on HTP over DOUBLE-STRUCK CAPITAL Z. We show that there is no algorithm to determine for any P(z(1), horizontal ellipsis ,z(9)) is an element of DOUBLE-STRUCK CAPITAL Z[z(1), horizontal ellipsis ,z(g)] whether the equation P(z(1), horizontal ellipsis ,z(g)) = 0 has integral solutions with z(9) > 0. Consequently, there is no algorithm to test whether an arbitrary polynomial Diophantine equation P(z(1), horizontal ellipsis ,z(11)) = 0 (with integer coefficients) in 11 unknowns has integral solutions, which provides the best record on the original HTP over DOUBLE-STRUCK CAPITAL Z. We also show that there is no algorithm to test for any P(z(1), horizontal ellipsis ,z(17)) is an element of DOUBLE-STRUCK CAPITAL Z[z(1), horizontal ellipsis ,z(17)] whether P(z1(2), horizontal ellipsis , z1(2), horizontal ellipsis z2(17)) = 0 has integral solutions, and that there is a polynomial Q(z(1), horizontal ellipsis , z(20)) is an element of DOUBLE-STRUCK CAPITAL Z[z(1), horizontal ellipsis ,z(20)] such that {Q(z1(2), horizontal ellipsis , z20(2)): z(1), horizontal ellipsis , z(20) is an element of DOUBLE-STRUCK CAPITAL Z} boolean AND {0, 1, 2, horizontal ellipsis } coincides with the set of all primes.