Obligations of the following organizations constituted under the laws of the United States shall be authorized investments:

(1) National Housing Administration.--Obligations issued pursuant to any housing act of the United States heretofore or hereafter enacted, but only if fully and unconditionally guaranteed as to principal and interest by the United States.

(2) Federal land banks.--Obligations of any Federal land bank and consolidated obligations, being the joint and several obligations of all Federal land banks, issued pursuant to the act of Congress of July 17, 1916 (39 Stat. 380), and its amendments and supplements heretofore or hereafter enacted.

(3) Federal home loan banks.--Obligations of any Federal home loan bank and consolidated obligations, being the joint and several obligations of all Federal home loan banks, issued pursuant to the act of Congress of July 22, 1932 (47 Stat. 725), and its amendments and supplements heretofore or hereafter enacted.

(4) Federal intermediate credit banks.--Consolidated obligations, being the joint and several obligations of all Federal intermediate credit banks, issued pursuant to the act of Congress of March 4, 1923 (42 Stat. 1456), and its amendments and supplements heretofore or hereafter enacted.

(5) Federal National Mortgage Association.--Obligations of the Federal National Mortgage Association issued pursuant to the act of Congress of August 2, 1954 (68 Stat. 612), and its amendments and supplements.

(6) Banks for cooperatives.--Obligations of the Central Bank for Cooperatives and consolidated obligations of the Central Bank for Cooperatives, and the regional banks for cooperatives issued pursuant to the provisions of the act of Congress of June 16, 1933, known as the "Farm Credit Act of 1933" (48 Stat. 257), and its amendments and supplements heretofore or hereafter enacted.

(7) Tennessee Valley Authority.--Obligations issued, assumed or guaranteed by the Tennessee Valley Authority.