C2/(N−m2)\rm{C^{2} /\left(N-m^{2}\right)}C2/(N−m2)
C2 N/m2\mathrm{C}^{2} \mathrm{~N} / \mathrm{m}^{2}C2 N/m2
C2 N2/m2\mathrm{C}^{2} \mathrm{~N}^2 / \mathrm{m}^{2}C2 N2/m2
C−N/m\mathrm{C}-\mathrm{N} / \mathrm{m}C−N/m