The principal technique in current use for teaching reading at the intermediate stage, a stage occurring between a beginning stage and an advanced stage, is that of graded readers. It is generally accepted that the achievement of fluency and that of a wider coverage of the language are desirable aims, and most teachers strive to obtain a large quantity of reading matter, often distinguishing between intensive and extensive reading. Two sources of difficulty exist: first, it is extremely difficult, in practice, for the teacher to meet the needs of each individual learner at the various different times that individuals actually become intermediate learners. Classwork presupposes that all learners progress from one stage to another at the same moment, which is not true. To try and get over this problem there is currently a wave of interest in individualization, that is, in providing within a common framework the opportunity for each individual learner to learn at least partly at his own rate In reading, this is promoted by the provision of numbers of separate materials lots of small books ,or leaflets, or cards -- which become longer and more complex. (Reading kits are a case in point. ) This trend is certain to increase. The second difficulty is that the grading of reading materials has often proved inadequate ,in two senses: (a) by being self-defeating, so that 'simplified' texts have frequently been 'simplified' out of all sensible meaning and (b) by the fact that many learners find vocabulary graded materials unappetizing: not that they can't learn from them, but that they won't. What is now being realized is that the grading of reading materials, and above all the choice of texts, must reflect not only characteristics of the language (vocabulary, grammar, etc. ) but also characteristics of the learner. What he is willing to read and what he is interested to read are products of his sex, age-group, level of education, degree of intellectuality, personal interests, etc. Reading materials are increasingly being designed to fit both the learner's level of proficiency in English and his reading interests. In doing so, they are providing the learner with the means of developing further command of the linguistic meanings of writing, enabling him to grasp informational and logical meaning, and perhaps starting him on the understanding of rhetorical and implicational meanings. The first paragraph mainly deals with the problem caused by ______.