Numerals in formulae

Roman numerals in names denote charges on ions Arabic numerals in formulas tell the number of atoms or ions present per formula unit. 

According to the correlation theorem (Press et ah, 1987, p. 383), the inverse Fourier transform of the product of spectrum of one function and the complex conjugate spectrum of another function is equal to correlation of these functions. Therefore, we can write the numerator in formula (15.38) as a cross correlation of the time derivatives of the back-propagated scattered field and the incident wavefield ... 

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