protected function addHyperlinks( \DOMDocument $chapter ) {
		$ln = $chapter->getElementsByTagName( 'a' );

		for ( $i = $ln->length; --$i >= 0; ) {  // If you're deleting elements from within a loop, you need to loop backwards
			$link = $ln->item( $i );
			if (
				$link->hasAttribute( 'name' ) &&
				in_array( $link->getAttribute( 'name' ), [ '_GoBack' ], true )
			) {
				// Delete hidden Shift+F5 editing bookmark
				$link->parentNode->removeChild( $link );
				continue;
			}
			if ( $link->hasAttribute( 'class' ) ) {
				$ln_id = $link->getAttribute( 'class' );
				if ( array_key_exists( $ln_id, $this->ln ) ) {
					// Add external hyperlink
					$link->setAttribute( 'href', $this->ln[ $ln_id ] );
				}
			}
		}

		return $chapter;
	}