<?xml version="1.0" encoding="utf-8" ?>
<Groups>
    <Group>1900s</Group>
    <Group>1910s</Group>
    <Group>1920s</Group>
    <Group>1930s</Group>
    <Group>1940s</Group>
    <Group>1950s</Group>
    <Group>1960s</Group>
    <Group>1970s</Group>
    <Group>1980s</Group>
    <Group>1990s</Group>
    <Group>Abstract</Group>
    <Group>Basic</Group>
    <Group>Civ</Group>
    <Group>Hitec</Group>
    <Group>Human</Group>
    <Group>Science</Group>
    <Group>Social</Group>
    <Group>Tools</Group>
</Groups>
