https://api.drupal.org/api/drupal/core%21modules%21migrate_drupal%21src%21Plugin%21migrate%21field%21d7%21NodeReference.php/10
NodeReference.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21migrate_drupal%21src%21Plugin%21migrate%21field%21d7%21NodeReference.php/class/NodeReference/10
class NodeReference | Drupal API
classdrupalapi