Given a list of integers, return a list of all values that appear more than once. The result should contain each duplicate value only once and be sorted in ascending order. For null input return null, for empty list return empty list.
Examples:
Input: numbers = [1, 2, 3, 2, 4, 3, 5]
Output: [2, 3]
Explanation: 2 and 3 appear more than once, returned in ascending order
Input: numbers = [1, 1, 1, 1]
Output: [1]
Explanation: 1 appears multiple times but is only included once in result
Input: numbers = [1, 2, 3]
Output: []
Explanation: No duplicates found, return empty list
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