Wikipedia:Book sources/styles.css

/* */ .wp-book-sources-collapse .mw-collapsible-toggle { background-color: var(--background-color-neutral-subtle, #efefef); border: 2px solid #fff; border-bottom: 1px solid #36b; padding: 5px; float: none; }

.wp-book-sources-collapse .mw-collapsible-content { border: 4px solid #fff; background-color: var(--background-color-neutral-subtle, #f7f7f7); padding: 10px; }

@media (min-width: 720px) { .wp-book-sources-other-langs { min-width: 35em; } }