ORS § 58.389
If the articles of incorporation or bylaws of a professional corporation organized for the purpose of practicing medicine do not provide a price or method of determining a price at which the corporation may purchase or redeem the shares, or at which its shareholders may purchase the shares, of a legally disqualified or deceased shareholder, and the corporation and shareholders or the shareholders have not provided the price or a method of determining the price by private agreement, then the price for the shares shall be the book value as of the end of the month preceding the disqualification or death of the shareholder, payable in cash or on such other terms as may be agreed to by the parties. Book value shall be determined from the books and records of the corporation in accordance with the regular method of accounting used by the corporation.
ORS 58.389