Filing Details

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. 4)* MDU Resources Group Inc. ----------------------------------------------------------------------------- (Name of Issuer) Common ----------------------------------------------------------------------------- (Title of Class of Securities) 552690109 ------------------------------------------- (CUSIP Number) December 31, 2018 -------------------------------------------------------------- (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [x] Rule 13d-1(b) [ ] Rule 13d-1(c) [ ] Rule 13d-1(d) *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). PAGE 1 OF 4 PAGES

-------------------------- ----------------- CUSIP NO.552690109 13G PAGE 2 OF 4 PAGES -------------------------- ----------------- ----------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Parnassus Investments 94-2943858 ----------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [_] (b) [_] N/A ----------------------------------------------------------------------------- 3 SEC USE ONLY ----------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION San Francisco, California - U.S.A. ----------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF 8,937,891 SHARES ---------------------------------------------------------- 6 SHARED VOTING POWER BENEFICIALLY OWNED BY 0 ---------------------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING 8,937,891 PERSON ---------------------------------------------------------- 8 SHARED DISPOSITIVE POWER WITH 0 ----------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 8,937,891 ----------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A ----------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 4.56% ----------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IA ----------------------------------------------------------------------------- Item 1(a) Name of Issuer: MDU Resources Group Inc. Item 1(b) Address of Issuer's Principal Executive Offices: 1200 West Century Avenue P.O. Box 5650 Bismarck, ND 58506 Item 2(a) Name of Person Filing: Parnassus Investments Item 2(b) Address of the Principal Office or, if none, Residence: 1 Market Steet, Suite 1600 San Francisco, CA 94105 Item 2(c) Citizenship: California - U.S.A. Item 2(d) Title of Class of Securities: Common Item 2(e) CUSIP Number: 552690109 Item 3 If the Statement is being filed pursuant to Rule 13d-1(b), or 13d-2(b), check whether the person filing is a: (e) [X] An investment advisor in accordance with section 240.13d-1(b)(1)(ii)(E) Item 4 Ownership: (a) Amount Beneficially Owned: 8,937,891 (b) Percent of Class: 4.56% PAGE 3 OF 4 PAGES (c) Number of shares as to which such person has: (i) sole power to vote or direct the vote: 8,937,891 (ii) shared power to vote or direct the vote: 0 (iii) sole power to dispose or to direct the disposition of: 8,937,891 (iv) shared power to dispose or to direct the disposition of: 0 Item 5 Ownership of Five Percent or Less of a Class: X Item 6 Ownership of More than Five Percent on Behalf of Another Person: Securities reported on this Schedule 13G are beneficially owned by clients of Parnassus Investments, which includes investment companies registered under the Investment Company Act. Item 7 Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company: Not applicable. Item 8 Identification and Classification of Members of the Group: Not applicable. Item 9 Notice of Dissolution of a Group: Not applicable. Item 10 Certification: By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purpose or effect. SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Dated: February 13, 2019 Parnassus Investments By: /S/ Marc C. Mahon ------------------------------------- Name: Marc C. Mahon Title: Chief Financial Officer PAGE 4 OF 4 PAGES