/**
 * DOI normalizer module
 *
 * Normalizes DOI identifiers by:
 * - Removing URL prefixes (doi.org, dx.doi.org)
 * - Trimming whitespace
 */
/**
 * Normalize a DOI identifier
 *
 * @param doi - DOI string, possibly with URL prefix
 * @returns Normalized DOI (10.xxx/xxx format)
 */
export declare function normalizeDoi(doi: string): string;
/**
 * Normalizes a PMID by removing the optional "PMID:" prefix and trimming whitespace.
 *
 * Supported formats:
 * - "12345678" -> "12345678"
 * - "PMID:12345678" -> "12345678"
 * - "pmid:12345678" -> "12345678"
 * - "PMID: 12345678" -> "12345678" (space after colon)
 *
 * @param pmid - The PMID string to normalize
 * @returns The normalized PMID (digits only) or empty string if invalid
 */
export declare function normalizePmid(pmid: string): string;
/**
 * Parses an ISBN input by removing the "ISBN:" prefix, hyphens, spaces, and uppercasing X.
 *
 * Supported formats:
 * - "ISBN:978-4-00-000000-0" -> "9784000000000"
 * - "isbn:4-00-000000-0" -> "4000000000"
 * - "ISBN: 978 4 00 000000 0" -> "9784000000000"
 * - "ISBN:400000000x" -> "400000000X" (uppercase X)
 *
 * @param isbn - The ISBN input string to parse
 * @returns The normalized ISBN (digits only, X uppercase at end for ISBN-10) or empty string if invalid
 */
export declare function parseIsbnInput(isbn: string): string;
/**
 * Normalizes an arXiv identifier by removing URL prefixes and arXiv: prefix.
 *
 * Supported formats:
 * - "2301.13867" -> "2301.13867"
 * - "2301.13867v2" -> "2301.13867v2"
 * - "arXiv:2301.13867" -> "2301.13867"
 * - "arxiv:2301.13867v2" -> "2301.13867v2"
 * - "https://arxiv.org/abs/2301.13867" -> "2301.13867"
 * - "https://arxiv.org/pdf/2301.13867" -> "2301.13867"
 * - "https://arxiv.org/html/2301.13867v2" -> "2301.13867v2"
 *
 * @param arxiv - The arXiv string to normalize
 * @returns The normalized arXiv ID or empty string if invalid input
 */
export declare function normalizeArxiv(arxiv: string): string;
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