The boundary problem of an ordinary linear differential system in the complex domain
Rudolph E. Langer · Transactions of the American Mathematical Society · 1939
f The reduction of differential systems «•' (*, \) = 2~L {^aA*) + bi,,(x, X)}uy(x, X), i= 1, 2, • • • , n, to form (1) is considered in G. D. Birkhoff and R. E. Langer, The boundary problems and developments associated with a system of ordinary linear differential equations of the first order, Proceedings of the American Academy of Arts and Sciences, vol.58 (1923), pp.72-74. 151* Throughout the paper square matrices of order n will be designated by means of German capital letters, and these letters will be used solely in this sense.The elements of a matrix will then generally be designated by the corresponding lower case italic letters, that is, in the manner %{x, X) s= (ai,j(x, X)).t The symbol 5,-,, will always be used in the sense â,-,, = 0, if ij*jl ii,/= 1, if i=j.