On formulas for the velocity of Stoneley waves propagating along the loosely bonded interface of two elastic half-spaces

► Formulas for the velocity of Stoneley waves propagating in two loosely bonded isotropic elastic half-spaces are derived. ► In order to derive these formulas the complex function method is employed. ► It is shown that if a Stoneley wave exists, then it is unique. ► By the obtained formulas, we can easily reproduce the results previously obtained by directly solving the secular equation.