duhkhera
duḥkhera kāraṇa — causes of suffering;
CC Adi 5.150
duḥkhera — of unhappiness;
CC Madhya 2.27
duḥkhera — of unhappiness;
CC Madhya 17.68
duḥkhera kāraṇa — the cause of unhappiness;
CC Antya 15.16