1. British Patent 151,016
2. British Patent 171,094; British Patent 181,014; British Patent 193,420; British Patent 201,906; British Patent 206,512; British Patent 213,567; British Patent 238,904; British Patent 240,840; British Patent 248,729
3. British Patent 187,605; British Patent 202,651; British Patent 208,761
4. British Patent 455,008