“…In the case of models belonging to the first class, the highest differentiation order of strain µ + η ∈ [1,2] , with η ∈ {α, β} , is greater than the highest differentiation order of stress, that is either γ ∈ [0, 1] in the case of Model I, in addition to 0 ≤ α ≤ β ≤ γ ≤ µ ≤ 1 and η ∈ {α, β, γ} , or γ ∈ [1,2] in the case of Models II -V, in addition to 0 ≤ α ≤ β ≤ µ ≤ 1 and (η, γ) ∈ {(α, 2α) , (α, α + β) , (β, α + β) , (β, 2β)} , while for models belonging to the second class differentiation orders of stress β ∈ [0, 1] and β + η ∈ [1,2] coincide with the highest differentiation orders of strain in addition to 0 ≤ α ≤ β ≤ 1, so that η = α, in the case of Model VI; η = β in the case of Model VII; and α = η = β, ā1 = a 1 + a 2 , and ā2 = a 3 in the case of Model VIII. Similar forms of the fractional Burgers models are checked for the thermodynamical consistency in [3,10], while the classical and different variants of fractional Burgers models, describing the flow of viscoelastic fluids in various geometries, are considered in [27,28,29,30,31,32,33,34].…”