The histone which does not form core of nucleosome

In the core of nucleosome there is copies each of ${\mathrm{H}}_2\mathrm{A}$, ${\mathrm{H}}_2\mathrm{B}$, ${\mathrm{H}}_3$and ${\mathrm{H}}_4$are present. ${\mathrm{H}}_1$ is present outside nucleosome and helps in fixing the DNA to core histones.