(b) The same censure is incurred by those who defend the aforementioned books, either materially (e.g., by saving them from destruction) or morally (e.g., by defending, praising, or recommending them). Ignorance excuses here as in the case of publishers. (c) The same censure is incurred by those who defend books of any author condemned by name through Apostolic letters. Hence, the censure does not apply to books condemned by a pontifical congregation nor to books condemned in a Papal Letter, if their title is not mentioned. Ignorance excuses here as in the previous case. (d) The same censure is incurred by those who knowingly keep or read any of the forbidden books mentioned so far in this paragraph. The sense to be attached to the words “keep or read” has been given above (see 862). Even crass and supine ignorance of law or penalty, provided it be not affected, as well as other causes that lessen imputability (see 40), excuse from this censure (Canon 2229, Sec.Sec.1, 2). (e) Excommunication not reserved is incurred _ipso facto_ by authors and publishers who are responsible for the printing without due authorization of books of Holy Writ, or of notes or commentaries on the Bible, even though the text be correct and the explanation orthodox. This censure is not incurred by those who are not responsible for the printing done, such as typesetters and readers. Ignorance, if not crass and supine, excuses here (Canon 2229, Sec.3). 867. Dangerous Schools.--With reference to their danger to faith, schools are of three kinds: (a) sectarian schools, in which heresy or infidelity is prescribed as part of the curriculum, and assistance at non-Catholic rites is required. Examples are colleges and universities supported by Protestant denominations, sectarian Sunday schools, Bible classes; (b) neutral schools (i.e., schools in which all religious teaching is forbidden and no recognition given to any denomination) whose spirit and teaching in secular branches is anti-religious or anti-Catholic. Examples are non-sectarian colleges or universities in which materialism is incidentally taught, or in which the faculty are freethinkers or bigots; (c) neutral schools in which no positive offense is given to religion or the Church. Examples are public schools in which only the profane sciences are taught, and care is exercised that neither the text-books nor the teachers shall be irreligious or interfere with the religious beliefs of others. Reducible to this category are mixed schools, that is, those which are open also to non-Catholics (Canon 1374). 868. The danger of the foregoing kinds of schools to the faith of pupils is as follows: (a) in the sectarian schools there is danger of heresy or infidelity, since the pupils are obliged to hear the defense of false doctrine and to join in the services of a false religion;