body {
    background: lightyellow;
    margin: 10%;
    text-align: justify
    }
h2, h3, h4, h5 {
    color: green;
    text-align: center
    }
hr {
    text-align: center
    }
ul {
    list-style: none
    }
.centre {
    text-align: center
    }
.external {
    color: blue
    }
.note {
    color: green
    }
.right {
    text-align: right
    }
a:link {
    color: blue;
    text-decoration: none
    }
link {
    color: blue;
    text-decoration: none
    }
a:visited {
    color: blue;
    text-decoration: none
    }
a:hover {
    color: red
    }
pre {
    font-size: 9pt
    }