Such trusts may be created by written instruments or by will. In the case of written instruments, the same shall be subscribed by the grantor or grantors and duly acknowledged as conveyances of real estate are acknowledged, and before the same shall become effective the beneficial interest therein shall be accepted by the Governor, if the state is the beneficiary, or by the governing body of any other beneficiary named therein, which power and authority of acceptance hereby is conferred upon the Governor and upon the governing bodies of the counties or municipalities. Provided, every trust made hereunder, if the state is the beneficiary, shall, prior to and as a condition precedent to its entry into force, be submitted to the Attorney General who shall determine whether the trust is in proper form and compatible with the laws of this state. The Attorney General shall approve any trusts submitted to him which he determines to be in proper form and compatible with the laws of this state. If approved, the said instrument or will, together with the written acceptance of the beneficial interest and approval of the Attorney General endorsed thereon, shall be recorded in the office of the county clerk of each county wherein is situated any real estate, or any interest therein, belonging to said trust, as well as in the county wherein is located the trust property or wherein are conducted its principal operations. In the case of any trust of which the State of Oklahoma is the beneficiary, a certified copy of such instrument or will and the instrument of acceptance shall be filed with the Secretary of State. Upon the acceptance of the beneficial interest by the beneficiary and approval by the Attorney General as hereinabove provided, the same shall be and constitute a binding contract between the State of Oklahoma and the grantor or grantors, or the executor of the estate of the testator, for the acceptance of the beneficial interest in the trust property by the designated beneficiary and the application of the proceeds of the trust property and its operation for the purposes, and in accordance with the stipulations of the trust instrument or will. Such trusts shall have duration for the term of duration of the beneficiary, or such shorter length of time as shall be specified in the instrument or will creating said trust.