TY  - BOOK
AU  - Heading,John
TI  - An introduction to phase-integral methods
U1  - 517.38 
PY  - 1962///
CY  - London
PB  - Methuen
KW  - Differential equations, Linear
KW  - Numerical solutions
KW  - Integrals
N1  - Includes bibliographical references and index
ER  -