Sorry, here’s the complete code.:
<?php $post_objects = get_field( 'field1' ); ?>
<?php if ( $post_objects ): ?>
<ul>
<?php foreach ( $post_objects as $post ): ?>
<?php setup_postdata( $post ); ?>
<li>
<a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
<li>
<?php endforeach; ?>
</ul>
<?php wp_reset_postdata(); ?>
<?php endif; ?>