Wikipedia - Wattora calorie

https://doi.org/10.1351/goldbook.C00784
Non-SI unit of energy. There are three differently defined calories: @T06311@ ($$\text{cal}_{\text{th}} = 4.184\ \text{J}$$), international steam table calorie ($$\text{cal}_{\text{IT}} = 4.1868\ \text{J}$$), $$15\ ^{\,\unicode{x26ac}}\text{C}$$ calorie ($$\text{cal}_{15} = 4.1855\ \text{J}$$), however only the symbol $$\text{cal}$$ is usually used.
Sources:
Green Book, 2nd ed., p. 112 [Terms] [Book]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 964 [Terms] [Paper]