How many of the following compounds have peroxy linkage?

$\begin{array}{l}{\mathrm{H}}_3{\mathrm{PO}}_5, {\mathrm{H}}_2{\mathrm{SO}}_5, {\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8, {\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_8,{ \mathrm{HNO}}_4, {\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_7\\ {\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_3, {\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_6\end{array}$

Here we have, 1 proxy linkage of $\mathrm{P}-\mathrm{O}-\mathrm{P}$ in ${\mathrm{H}}_3{\mathrm{PO}}_5$, 1 proxy linkage of $\mathrm{S}-\mathrm{O}-\mathrm{S}$ in ${\mathrm{H}}_2{\mathrm{SO}}_5$, 1 proxy linkage of $\mathrm{S}-\mathrm{O}-\mathrm{S}$ in ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8$, 

The compounds which have peroxy linkage are,

${\mathrm{H}}_3{\mathrm{PO}}_5, {\mathrm{H}}_2{\mathrm{SO}}_5, {\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8, {\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_8,{ \mathrm{HNO}}_4$.