“…When this algebraic method is used for numerical differentiation problem, thanks to the proposed integral formulae, it also refers to the differentiation by integration method well known for the Lanczos generalized derivative (see [13] p. 324). The obtained algebraic differentiators have been used to design algebraic nonasymptotic observers for linear and non-linear systems (see, e.g., [14,15,17,18,19]). In the linear case [14,15,16], the proposed differentiators were obtained via the differential equations which define the linear systems.…”