body.view-article div.article-details div[itemprop="articleBody"] h2 {
    font-size: 42px !important;
}

body.view-article div.article-details div[itemprop="articleBody"] h3 {
    font-size: 32px !important;
}

body.view-article div.article-details div[itemprop="articleBody"] h4 {
    font-size: 24px !important;
}