That's right - no admission without a team sheet. Believe it or not, 40p was the admission price in those days.
When it was played on a Sunday...
For the Sunday games in 1973-74 you had to buy an admission sheet to enter the ground due to the Sunday trading laws at the time. Clubs also had to offer a free turnstile for those who did not want to pay. I have all four of the admission sheets for home games (priced at 40p for adults and 20p for children on the Sincil Bank side).
Not sure if this also applied for the Sunday games in the early 1980s.