characterizing the binding of quarks inside the hadron [@vs].

The paper is organized as follows. In agreement with the general picture given above, we describe the scheme for the construction of OPE for the total width of baryons containing two heavy quarks with account of corrections to the spectator widths in Section 2. The procedure for the estimation of non-perturbative matrix elements of operators in the doubly heavy baryons is considered in Section 3 in terms of non-relativistic heavy quarks. Section 4 is devoted to the numerical evaluation and discussion of parameter dependence of lifetimes of doubly heavy baryons. We conclude in section 5 by summarizing our results.

Description of the method
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In this section we describe the approach used for the calculation of total lifetimes for the doubly heavy baryons, originally formulated in [@DHD1; @DHD2], together with some new formulae, required for the evaluation of nonspectator effects in the decays of other[^5] baryons in the family of doubly heavy baryons, not considered previously.

The optical theorem along with the hypothesis of integral quark-hadron duality, leads us to a relation between the total decay width of heavy quark and the imaginary part of its forward scattering amplitude. This relationship, 