3-NIRVANA-user-guide/3.2-User-interfaces.md

@@ -922,7 +922,7 @@ range $[0,1]$. The mesh of the superblock is indexed by
 **Important:** The species number densities must be consistently defined
 along with the mass density because of the conservation condition
 
-$$\sum_s(\mu_s+\mu_e q_s)n_s = \varrho/m_u,\quad s=0,\mathtt{_C.species}-1$$
+$$\sum_s(\mu_s+\mu_e q_s)n_s = \varrho/m_u,\quad s=0,\mathtt{\_C.species}-1$$
 
 where $\mu_s$, $q_s$ and $\mu_\mathrm{e}$ are the molecular weight,
 charge of the s-th specie and the electron weight, respectively. In