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f ( x ) = ∫ R d ∑ a ⊂ I Φ ( x a ) d x ∫ R d ∑ a ⊂ I Φ ( x a ) d x {\displaystyle f(x)={\frac {\int _{R^{d}}\sum \limits _{a\subset I}\Phi (x_{a})dx}{\int _{R^{d}}\sum \limits _{a\subset I}\Phi (x_{a})dx}}}
