TeX source:
S=m\left( c\ln{\frac{T_v}{T_s}}+\frac {r}{T_v}+c_p\ln{\frac{T}{T_v}}\right)=n\left( \hat c\ln{\frac{T_v}{T_s}}+\frac {\hat r}{T_v}+\hat c_p\ln{\frac{T}{T_v}}\right)