 Another problem with the above elaboration is that the “well-known” relations  (5)  are actually false if energy \(\boldsymbol{E}\) and action \(\boldsymbol{J}\) are to be positive operators (Jordan 1927). In that case, self-adjoint operators \(\boldsymbol{t}\) and \(\boldsymbol{w}\) do not exist and inequalities analogous to  (9)  cannot be derived. Also, these inequalities do not hold for angle and angular momentum (Uffink 1990). These obstacles have led to a quite extensive literature on time-energy and angle-action uncertainty relations (Busch 1990; Hilgevoord 1996, 1998, 2005; Muga et al. 2002; Hilgevoord and Atkinson 2011; Pashby 2015).