There are discussed two methods to distinguish the coalescence from thermal production of light nuclei. At first the hadron-deuteron correlation function is shown to carry information about an origin of deuterons, whether they are emitted from a fireball together with all other hadrons or formed due to final state interactions after nucleons left the fireball. Secondly, it is proposed to measure the yield of an exotic nuclide 4Li and compare it the yield of 4He. The coalescence and thermal models predict a significantly different ratio of the yields of 4Li to 4He. A measurement of 4Li is discussed.