The question of precisely which elements should be placed in group 3 of the periodic table has been debated from time to time, with apparently no resolution up to this point.  This question has also received a recent impetus from several science news reports following an article in Nature in which the measurement of the ionization energy of the element lawrencium was reported for the first time. [2,3]
We believe that this question is of considerable importance for chemists and physicists, as well as students of the subjects. Students and instructors are typically puzzled by the fact that published periodic tables show variation in the way that group 3 of the periodic table is displayed. An IUPAC task group has now been formed in order to make a recommendation regarding the membership of group 3 of the periodic table.
Various forms of evidence have been put forward in support of each version of group 3, appealing to chemical as well as physical properties, spectral characteristics of the elements, and criteria concerning the electronic configurations of their atoms. The task group will aim to evaluate all this evidence in order to reach a conclusion that encompasses these different approaches. 
It is proposed that IUPAC should make an official recommendation in favor of the composition of group 3 of the periodic table as consisting either of
(1) the elements Sc, Y, Lu and Lr, or
(2) the elements Sc, Y, La and Ac.
It should be stated categorically that the task group does not intend to recommend the use of a 32-column periodic table or an 18-column. This choice is a matter of convention, rather than a scientific one, and should be left to individual authors and educators. As Jeffery Leigh has asserted recently, IUPAC has not traditionally taken a view as to the correctness of one or the other periodic table and there is no such thing as an officially approved IUPAC periodic table.  We will only concern ourselves with the constitution of group 3. Once this is established, one is free to represent the periodic table in an 18 or 32 column format. The conclusions of the task force will form the basis for a report to appear in Pure and Applied Chemistry.
The task group welcomes comments on this project.
R.W. Clark, G.D. White, J. Chem. Educ., 85:497, 2008; W.B. Jensen, J. Chem. Educ., 59:634-636, 1982; L. Lavelle, J. Chem. Educ., 85:1482–1483, 2008; E.R., Scerri, J. Chem. Educ., 86:1188-1188, 2009; W.B. Jensen, J. Chem. Educ., 85:1491, 2008; E.R. Scerri, Chem. Int., 34(4):28-31, 2012, www.iupac.org/publications/ci/2012/3404/ud.html; E. Scerri, A Very Short Introduction to the Periodic Table, Oxford University Press, Oxford, 2013; W.B. Jensen, Foundations of Chemistry, 17:23-31, 2015.
D. Castelvecchi, Exotic Atom Struggles to Find Its Place in the Periodic Table, Nature, 2015, (8 April), doi:10.1038/nature.2015.17275 ; J. Kemsley, Lawrencium Ionization Energy Measured, Chem. & Eng. News, 93:8, 2015; M. Gunther, Lawrencium Experiment Could Shake Up the Periodic Table, Chemistry World, 9 April 2015, www.rsc.org/chemistryworld/2015/04/lawrencium-exeriment-could-shake-periodic-table ; R. Gray, Is the Periodic Table Wrong? Elements May Need to be Reordered After Scientists Find Lawrencium Looks Out of Place, Daily Mail, 2015, 10 April, www.dailymail.co.uk/sciencetech/article-3033570/Is-periodic-table-WRONG-Elements-need-reordered-scientists-Lawrencium-looks-place.htmlCrossref
L.D. Landau, E.M. Lifshitz, E.M., Quantum Mechanics, Pergamon, London, 1959, p. 245 footnote; W. F. Luder, J. Chem. Educ., 20, 21, 1943; D.C. Hamilton, M.A. Jensen, Phys. Rev. Letters, 11:205, 1963; B.T. Matthias, W.H. Zacharisen, G.W. Webb, J.J. Englehardt, Phys. Rev. Letters,18:781, 1967; V.M. Christyakov, Zh. Obshch. Khim.,38(2):209, 1968.Google Scholar
J. Leigh, Chem. Int., 31(1):4-6, 2009. www.iupac.org/publications/ci/2009/3101/1_leigh.html