WordPress Comments Fields with Bootstrap classes

comments.php

<div class="row">
    <div class="col-md-8 comment-form">
    <?php 
        $fields = array(

            'author' =>
                '<div class="form-group"><label for="author">' . __( 'Name', 'domainreference' ) . '</label> <span class="required">*</span> <input id="author" name="author" type="text" class="form-control" value="' . esc_attr( $commenter['comment_author'] ) . '" required="required" /></div>',

            'email' =>
                '<div class="form-group"><label for="email">' . __( 'Email', 'domainreference' ) . '</label> <span class="required">*</span><input id="email" name="email" class="form-control" type="text" value="' . esc_attr(  $commenter['comment_author_email'] ) . '" required="required" /></div>',

            'url' =>
                '<div class="form-group last-field"><label for="url">' . __( 'Website', 'domainreference' ) . '</label><input id="url" name="url" class="form-control" type="text" value="' . esc_attr( $commenter['comment_author_url'] ) . '" /></div>'

        );

        $args = array(

            'class_submit' => 'btn btn-block btn-lg btn-info',
            'label_submit' => __( 'Submit Comment' ),
            'comment_field' =>
                '<div class="form-group"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label> <span class="required">*</span><textarea id="comment" class="form-control" name="comment" rows="2" required="required"></textarea></div>',

            'fields' => apply_filters( 'comment_form_default_fields', $fields )

        );

        comment_form( $args ); 

    ?>
    </div>
</div>

Nicely done. Thank you.

Welcome :)