public function injectHouseStyles( $css ) {

		$scan = [
			'/*__INSERT_PDF_HOUSE_STYLE__*/' => get_theme_root( 'pressbooks-book' ) . '/pressbooks-book/assets/legacy/styles/_pdf-house-style.scss',
			'/*__INSERT_EPUB_HOUSE_STYLE__*/' => get_theme_root( 'pressbooks-book' ) . '/pressbooks-book/assets/legacy/styles/_epub-house-style.scss',
			'/*__INSERT_MOBI_HOUSE_STYLE__*/' => get_theme_root( 'pressbooks-book' ) . '/pressbooks-book/assets/legacy/styles/_mobi-house-style.scss',
		];

		foreach ( $scan as $token => $replace_with ) {
			if ( is_file( $replace_with ) ) {
				$css = str_replace( $token, \Pressbooks\Utility\get_contents( $replace_with ), $css );
			}
		}

		return $css;
	}