<div class="b-article">
<div class="b-article__main-section">...</div>
<div class="b-article__aside">...</div>
</div>
<!-- its accompanying Less stylesheet -->
.b-article {
.makeRow(); // Mixin provided by Bootstrap
&__main-section {
.makeColumn(10); // Mixin provided by Bootstrap
}
&__aside {
.makeColumn(2); // Mixin provided by Bootstrap
}
}