Spline — Single knots at 1/3 and 2/3 establish a spline of three cubic polynomials meeting with C2 continuity. Triple knots at both ends of the interval ensure that the curve interpolates the end points
Photo Credit: By Garry R. Osgood - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4314548

Fürst Alexander Johann Cuza — Lithographie von Josef Kriehuber, 1861
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=38794754

University Square - University of Iași —
Photo Credit: By Argenna - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10986074

Logo Alexandru-Ioan-Cuza-Universität Iași —
Photo Credit: By Unknown author - www.uaic.ro, Public Domain, https://commons.wikimedia.org/w/index.php?curid=48474814

Isaac Jacob Schoenberg in 1971 —
Photo Credit: By Jacobs, Konrad - https://opc.mfo.de/detail?photo_id=3723, CC SA 1.0, https://commons.wikimedia.org/w/index.php?curid=6162598

Theophilos on gold solidus —
Photo Credit: By Classical Numismatic Group, Inc. http://www.cngcoins.com, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=347700

Michael II the Amorian — Constantinople mint. Struck 821-829. Crowned and draped facing bust of Michael, wearing short beard
Photo Credit: By Classical Numismatic Group, Inc. http://www.cngcoins.com, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=15057665

Proclamation of Leo V as emperor — Miniature from the Madrid Skylitzes
Photo Credit: By from the Middle Ages, unknown - en:Madrid Skylitzes, Public Domain, https://commons.wikimedia.org/w/index.php?curid=15203759

Battle of Versinikia — The battle of Versinikia from the 14th century Bulgarian copy of the Manasses Chronicle.
Photo Credit: By Original: Constantine Manasses - Scanned from book "Miniatures from the Manasses Chronicle", Ivan Duichev, "Bulgarski hudojnik" Publishing house, Sofia, 1962, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3511981

Battle of Versinikia — The Bulgarians annihilate the Byzantine army at Versinikia.
Photo Credit: By John Skylitzes - Madrid Skylitzes, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10481736

Krum's Advances — Territorial expansion of Bulgaria during the reign of Khan Krum (803-814)
During his reign the Bulgarian territory doubled in size, spreading from the middle Danube to the Dnieper and from Odrin to the Tatra Mountains.
Photo Credit: By Kandi - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=3211315