필요�?서식 자료 역시 서식 자료실을 통해�?무료�?내려받을 �?있다�?합니�? If a grammatical principle which is additional to 서툴�?is a vowel �?and there is no other alternative besides a vowel �?then that grammatical basic principle can't be extra to 서툴�? Any grammatical basic principle whe