(en) Brad M. S. Hanseret al., «HST Observations of the White Dwarf Cooling Sequence of M4», The Astrophysical Journal Supplement Series, vol.155, no2, , p.551-576 (ISSN0067-0049 et 1538-4365, DOI10.1086/424832, résumé, lire en ligne).
(en) Nathaniel Walton, «Conservation of Energy in an Isolated System», Research and reviews: journal of pure and applied physics, vol.10, no5, , p.19–20 (ISSN2320-2459, DOI10.4172/2320-2459.10.5.005).
(en) Brad M. S. Hanseret al., «HST Observations of the White Dwarf Cooling Sequence of M4», The Astrophysical Journal Supplement Series, vol.155, no2, , p.551-576 (ISSN0067-0049 et 1538-4365, DOI10.1086/424832, résumé, lire en ligne).
(en) Brad M. S. Hanseret al., «HST Observations of the White Dwarf Cooling Sequence of M4», The Astrophysical Journal Supplement Series, vol.155, no2, , p.551-576 (ISSN0067-0049 et 1538-4365, DOI10.1086/424832, résumé, lire en ligne).
(en) Nathaniel Walton, «Conservation of Energy in an Isolated System», Research and reviews: journal of pure and applied physics, vol.10, no5, , p.19–20 (ISSN2320-2459, DOI10.4172/2320-2459.10.5.005).