/**
 * Validates an ISBN (International Standard Book Number), supporting both ISBN-10 and
 * ISBN-13 formats. Ensures that the ISBN has the correct format and checksum. Any dashes
 * or whitespace are ignored.
 *
 * @param {string} isbn - The ISBN as a string.
 * @returns {boolean} `true` if the ISBN is valid; `false` otherwise.
 */
export declare function isIsbnValid(isbn: string): boolean;
/**
 * Validates an ISBN (International Standard Book Number), supporting both ISBN-10 and
 * ISBN-13 formats. Ensures that the ISBN has the correct format and checksum. Any dashes
 * or whitespace are ignored.
 *
 * @param {string} isbn - The ISBN as a string.
 * @returns {boolean} `true` if the ISBN is invalid; `false` otherwise.
 */
export declare const isIsbnInvalid: (isbn: string) => boolean;
/**
 * Determines the region name associated with an ISBN based on its prefix. Region names are all in Polish.
 *
 * @param {string} isbn - The ISBN as a string.
 * @returns {string | null} The region name as a string, or `null` if not recognized.
 */
export declare function getRegionNameFromIsbn(isbn: string): string | null;