NCBI element sup

Abstract	false (This can be used in an instance)
Nillable	false (Instance values cannot use xsi:nil)
Declared Namespaces	xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns:xlink=http://www.w3.org/1999/xlink xmlns:xs=http://www.w3.org/2001/XMLSchema xmlns:mml=http://www.w3.org/1998/Math/MathML

<xs:element name="sup">
    <xs:complexType mixed="true">
        <xs:choice minOccurs="0" maxOccurs="unbounded">
            <xs:element ref="email"/>
            <xs:element ref="ext-link"/>
            <xs:element ref="uri"/>
            <xs:element ref="inline-supplementary-material"/>
            <xs:element ref="related-article"/>
            <xs:element ref="bold"/>
            <xs:element ref="italic"/>
            <xs:element ref="monospace"/>
            <xs:element ref="overline"/>
            <xs:element ref="sc"/>
            <xs:element ref="strike"/>
            <xs:element ref="underline"/>
            <xs:element ref="inline-graphic"/>
            <xs:element ref="private-char"/>
            <xs:element ref="inline-formula"/>
            <xs:element ref="tex-math"/>
            <xs:element ref="mml:math"/>
            <xs:element ref="abbrev"/>
            <xs:element ref="named-content"/>
            <xs:element ref="fn"/>
            <xs:element ref="target"/>
            <xs:element ref="xref"/>
            <xs:element ref="sub"/>
            <xs:element ref="sup"/>
        </xs:choice>
        <xs:attribute name="arrange">
            <xs:simpleType>
                <xs:restriction base="xs:token">
                    <xs:enumeration value="stack"/>
                    <xs:enumeration value="stagger"/>
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
    </xs:complexType>
</xs:element>

element {}sup

Source