The existence of unwritten or purely oral languages without a standardized writing system is a basic, widely recognized linguistic fact that requires no academic citation.
The claim that there are modern spoken languages completely lacking a standardized spelling system is a well-established linguistic fact (many of the world's thousands of languages are strictly oral or lack standardized orthographies). Following Step 0, statements that are directly true by definition or everyday observation are classified as COMMON_KNOWLEDGE, requiring no citation or paper matching.