.book .book-summary .chapter > .articles {
    overflow: hidden;
    max-height: 0px;
}

.book .book-summary .chapter.expanded > .articles {
    max-height: 9999px;
}

.book .book-summary ul.summary li a,
.book .book-summary ul.summary li span {
    cursor: pointer;
}

.book .book-summary .exc-trigger {
    float: right;
}
.book .book-summary .exc-trigger:before {
    content: "\f054";
}

.book .book-summary .expanded > a .exc-trigger:before,
.book .book-summary .expanded > span .exc-trigger:before {
    content: "\f078";
}

.book .book-summary .summary .hidden-chapter {
    display: none;
}