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$\newcommand{\matrixelement}[3]{\langle#1|#2|#3\rangle}$
$\newcommand{\dd}[2][]{\frac{d#1}{d#2}}$
\begin{eqnarray} \int d^4y_1 \int d^4y_2\matrixelement{0}{T(\phi(x_1)\phi(x_2) {L}(y_1) {L} (y_2)}{0}; \end{eqnarray}
\[ \int d^4y_1 \int d^4y_2\matrixelement{0}{T(\phi(x_1)\phi(x_2) {L}(y_1) {L} (y_2){0}\]
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