gas for densities between about 100 and $10^5$ cm$^{-3}$ [e.g., @osterbrock89]. Unfortunately, both components of these doublets are very near in wavelength to each other, which makes it challenging to isolate the two lines in most of our targets, given their broad intrinsic widths of typically $\sim$800 km s$^{-1}$ (Appendix \[sec:individualobjects\] gives the FWHM for individual targets), moderate spectral resolution of R$=$1500 provided by the H$+$K grating, presence of night-sky line residuals, and relatively faint line fluxes.

In spite of this, we were able to identify and resolve the \[OII\]$\lambda\lambda$3726,3729 doublet in RC J0311$+$0507 (§\[ssec:indrcs0311\]) with a line ratio of F(3727)/F(3729)=0.96, which suggests an electron density of 350 cm$^{-3}$ for the best-fit value of the line ratio of F(3727)/F(3729)=0.96 [see also Table \[tab:emlines\] @osterbrock89]. To our knowledge, this is the first estimate of the electron density in an AGN host galaxy at z$\ge$4. In USS 0211-122 at z$=$2.34, we find a \[SII\]$\lambda\lambda$6716,6731 ratio of 1.3, corresponding to an electron density of 370 cm$^{-3}$ (Table \[tab:emlines\]). In MRC 0114$-$211 at z$=$1.4, we find a line ratio of 1.25 between the two \[SII\] doublet lines, which corresponds to a best-fit value of $n_e=310$ cm$^{-1}$. @nesvadba06a and @nesvadba08 previously found electron densities of 