What rules apply to guides for visually impaired skiers?

From Nordiq Canada's Para-Nordic Race Event Guidelines (2019 edition), which follow the IPC Nordic Skiing rules:

• Visually impaired skiers (B1-B3) ski with two skis, two poles and a guide. A guide is obligatory for B1 athletes and optional for B2 and B3 athletes.
• The guide gives visual and/or auditory guidance and is responsible for the safety of the skier. The guide may lead, follow or ski alongside, and is treated as a competitor for most rules (technique, obstruction and so on). Guides normally wear a yellow or orange bib printed with a "G".
• Guiding must be by voice only. Audio communication is permitted and a guide may use an amplifier, except in the biathlon range zone of silence.
• Normally there is no physical contact during the race, except that for safety reasons the guide may hold the athlete (normally by one arm or one pole), for example in fast downhills, corners and the shooting range. The guide may not hold up, push or pull the athlete, even on downhills.
• You may use more than one guide in a competition, but only one at a time. The athlete must complete the full course.
• At the finish, the time is recorded when the athlete crosses the line. No time is recorded for guides.
• At the start, the athlete must be behind the start wand, but the guide can be in front, beside or following.