# Introduction

This library provides a C library designed as a API-compatible replacement for the C SLALIB library (SUN/67) and uses a GPL licence so is freely redistributable. Where possible the functions call equivalent SOFA routines (Hohenkerk, C., 2011, Scholarpedia, 6, 11404) and use current IAU 2006 standards. This means that any functions that rely on nutation or precession will return slightly different answers to the SLA functions.