“…l for all t ą 0, x, y P R d , y ‰ 0. Indeed, taking (11) for granted, and using Proposition 10(i): e ´tP ε i Ñ e ´tΛr strongly in L r for some tε i u Ó 0 and every r Psr c , 8r, we obtain x1 S1 , e ´tΛr 1 S2 y ď Cx1 S1 , e ´tA ϕ t 1 S2 y for all compact S 1 , S 2 Ă R d . Since, by Theorem 2, e ´tΛr is an integral operator for every t ą 0 with integral kernel e ´tΛ px, yq, we obtain by the Lebesgue Differentiation Theorem, possibly after changing e ´tΛ px, yq on a measure zero set in R d ˆRd , that e ´tΛ px, yq ď Ce ´tA px, yqϕ t pyq for all t ą 0, x, y P R d , y ‰ 0, and so Theorem 3 follows.…”