स्वेच्छा से
In order to be influential, group norms should be volitionally accepted by members.

स्वेच्छापूर्वक
In order to be influential, group norms should be volitionally accepted by members.

स्वेच्छया
In order to be influential, group norms should be volitionally accepted by members.

स्वेच्छतः
In order to be influential, group norms should be volitionally accepted by members.