모든 콘텐�?기사)�?저작권법의 보호�?받는 �? 무단전재, 복사, 배포 등을 금합니다. If a grammatical principle which is extra to 서툴�?is often a vowel �?and there is no other solution in addition to a vowel �?then that grammatical principle can not be additional to 서툴�? Any grammatical basic