When context makes the quantifier clear, English allows for its dropping. Standardization requires that you to put it back.
| ENGLISH SENTENCE | STANDARDIZED TRANSLATION |
| A book is missing |
Some books are missing (We know that not all books are missing.) |
| A book is something to read |
All books are things to read (Here context makes the universality clear.) |
| A student is logical |
Some students are logical persons or All students are logical persons (Which is correct will depend on context.) |