'a third institution' is correct and usable in written English.
It can be used to refer to a third organization, place, or group. For example, "The new law will be enforced by a third institution outside of the government."
A third institution located in the same region also had just one of these architectural elements.
Last summer, recalls Meryl Levitz, president and chief executive of the Philadelphia tourism marketing organization, the leaders of the Barnes, the Philadelphia Museum of Art and a third institution, the Pennsylvania Academy of the Fine Arts, sought a meeting with her organization and city officials.
Jazz and the public dance was a third institution in our lives, and a vital one; and though Jimmy was far from being a preacher, he was, as official floor manager or master-of-the-dance at Slaughter's Hall, the leader of a public rite.
[Update 2: What's consistent in both statements this week is that Zuckerberg sees Facebook as a third institution that incorporates values of both tech and media: a place for "public discourse".
A brain tumor patient operated and diagnosed in a third institution as anaplastic astrocytoma (AA) (Fig. 1a d) was referred for further treatment, and the local investigator was considering to enter the patient in the CATNON study.
A fourth institution, government, "was the next to fall".
Under the overhaul plan, the government has divided Kabul Bank into a "good bank" with its deposits, good loans and other assets, and a second institution that will handle the hundreds of millions of dollars in bad loans, Afghan banking officials said.
A Consultative Committee was established alongside the High Authority, as a fifth institution representing civil society.
A fourth institution, the University of Montana, is required by the U.S. Department of Justice to issue one or more annual climate survey as a result of the agency's investigation into the school and the town of Missoula, Mont.
A second institution reported on the need to have a multidisciplinary advisory group to establish clear guidelines for which patients should be offered NGS testing as a lesson learned.
Because of all that, the objective of this study was to describe the attachment expressions and behaviors of mothers and newly born hospitalized in an Intensive Care Unit within a third level institution in Barranquilla, Colombia.
