Historical clue formulations

• Planets like ours, in sci-fi — 2018-03-25
• Cerium and samarium are rare ones — 2013-03-14
• "At the ___ Core," 1976 sci-fi film — 2008-02-10
• Brownish pigments — 2005-01-16
• "___ crammed with heaven": E. B. Browning — 2002-04-26
• Agronomists' studies — 1994-09-17
• Kipling's "When _____ Last Picture Is Painted" — 1993-12-18